Appendix, No. VI. Account of the Expense of Erecting the Skerryvore… — Account of the Skerryvore Lighthouse by Alan Stevenson

Appendix, No. VI. Account of the Expense of Erecting the Skerryvore Lighthouse and of the Subsidiary Works.

Establishment at Hynish.
	Wages of the different workmen quarrying and dressing the stones, and building the dwelling-houses, barracks, storehouses, inclosure and subdivision dykes, draining and trenching the ground, &c., at Hynish, and the wages of joiners preparing and fitting up the joiner work,					£2996	7	7
	Timber, pavement, bricks, ironmongery, glass, &c., &c., used in the erections,					1376	16	9	¹⁄₂
	Slater, plaster, and plumber work of the houses,					436	1	0
	Paid the tenant of Hynish for a barn which was used as a barrack to accommodate the workmen when they first landed at Tyree,					13	0	0
										£4822	5	4	¹⁄₂
	Note.—Although these buildings had been erected for the purposes of the works, yet the greater part of them were designed to serve as part of the permanent accommodation required at Tyree in connection with the Lighthouse Establishment, and have accordingly been so applied.
Rock Barrack, No. 1.
	Cost of the barrack on the Rock, which was destroyed, including the contractor’s account for extra work, &c.,					£742	17	7
	Lead for running up the bats and for other purposes about the barrack,					14	11	6	¹⁄₂
	A smith’s forge, bellows, anvil, and smith’s tools used at Rock in erecting the barrack,					32	19	1	¹⁄₄
										790	8	2	³⁄₄
Rock Barrack, No. 2.
	Cost of the carpenter and joiner work on the second barrack, the expense of fitting and erecting it at Greenock, the wages of four joiners and a smith, furnished by the contractor to assist in its erection at Skerryvore, including sundry other minor charges,					£911	14	4
	Cost of the iron-work of the barrack,					369	11	8
	Lead for running up the bats and protecting the timber of cooking apartment, &c.,					29	11	10
	Cooking apparatus for the cook-room of barrack, sheet-iron smoke tube, cooking utensils, &c.,					54	16	6
	Bedding for beds of barrack,					90	9	1
	Expense of upholding and making sundry small repairs on the barrack since its erection,					22	18	6	¹⁄₂
										1479	1	11	¹⁄₂
	Cost of the furniture, bedding, and other utensils required for the dwelling-houses, barracks, &c., connected with the different establishments of the works,									830	19	2
Establishment at North Bay.
	Wages of the quarriers, masons, joiners, &c., quarrying stones, building the barracks, storehouses, &c., &c., and fitting up the joiner work,					£378	11	9
	Timber and other furnishings for the erections, the expense of making the doors and windows, including furnishings required for erecting the habitable part of Skerryvore Barrack at North Bay as a temporary accommodation for the workmen, and sundry other charges,					361	4	7
	Sundry furnishings—such as utensils for provision store, smithy, &c.,					13	2	5
										752	18	9
Quarries at North Bay.
	Cost of rails and timber for railway and timber, &c., for shipping-pier at North Bay,					£131	5	1
	Wages of workmen who were employed at quarries in North Bay, quarrying the lighthouse blocks, constructing the pier, railway, &c.,					1752	5	3
										1883	10	4
Temporary Wharf and Railway at the Skerryvore Rock.
	Cost of timber used in the wharf and railway at the Skerryvore Rock,					£103	18	6
	Iron bats, bolts, &c., for fastening the timber, rails for railway, and sundry furnishings connected with an apparatus for blasting under water,					119	7	6
	Wages of the workmen constructing the railway, fastening the timber of wharf, &c.,					34	10	5
										257	16	5
Excavation at Rock and Platform, &c.
	Wages of the workmen excavating the foundation for the Lighthouse Tower, on the Skerryvore Rock,					£609	2	3	¹⁄₂
	A portable forge, and other smith’s tools, used at the rock for this work,					21	15	10
	Wages of the workmen excavating the site of a platform at the workyard in Hynish, and quarrying and dressing stones for sill of platform,					£107	16	5
	Cost of freestone from Garscube Quarry, Glasgow, for part of the sill of platform,					24	14	0
										763	8	6	¹⁄₂
Dressing Lighthouse Blocks.
	Wages of masons, including the assistance of labourers, carters, &c., in dressing the blocks for the Lighthouse Tower at Hynish,					£8589	8	7	¹⁄₂
	Timber for moulds of the various blocks, and the joiners’ wages making the moulds,					384	18	10
	Timber, &c., and wages of joiners in erecting sheds for the masons,					955	4	5
										9929	11	10	¹⁄₂
	Expense of victualling the workmen and others who were employed at the rock during the operation of the whole works,									1503	18	6
Implements and Tools for Masons, Smiths, &c.
	Amount paid to sundry persons for the implements and tools used by the workmen in all the departments of the works,					£1176	9	6	¹⁄₂
	Wages of the smiths and their hammermen keeping these tools in repair and making others,					908	16	5
										2085	5	11	¹⁄₂
Machinery for the Works at the Rock, Hynish, and North Bay.
	Cost of cranes, crabs, winches, trucks, iron blocks, chains, rope-guys, &c., with sundry other furnishings connected with these articles,					£1516	9	5
	1 Woolwich or sling-cart, a janker for wood, and four jack-screws,					89	6	4
	Large balance crane used in building the Lighthouse Tower,					533	10	0	¹⁄₂
	Hoisting beams or needles, and a pair of strong sheer-poles, used in building the Lighthouse Tower,					42	11	2
										2181	16	11	¹⁄₂
Cartage Account.
	Cost of 3 large draught horses and a pony, for the use of the works,					£127	9	10	¹⁄₂
	Carts and stable utensils,					65	14	2	¹⁄₂
	Harness and other furniture, and keeping them in repair,					52	2	3	¹⁄₂
	Provender for the horses for seven years,					858	14	8
										1104	1	0	¹⁄₂
Mortar Account.
	Cost of the lime which was used for all the departments of the works,					£331	9	8
	Pozzolano which was used for the building of the Lighthouse Tower, excepting a small portion for the works of the harbour or dock,					376	16	4
	Mastic, cements, and stucco,					39	6	10
	Wages of labourers grinding and sifting Pozzolano at Hynish, and burning and sifting a portion of the lime,					121	18	8
	Packages to contain Pozzolano, to prevent its admixture with other cargo when on board ship,					20	0	1
										889	11	7
Signal Tower at Hynish.
	Expense of quarrying, dressing, and building the stones, and executing the joiner work of the Signal Tower at Hynish,					£370	13	2
	Pavement and bricks for the interior,					32	13	1
	Cast-iron floor, with lintels and sole plates for windows, and cast-iron supports for do.,					110	13	4
	Timber for joisting of floors, lining of walls and windows, including the glazing of them, a wooden trap, flag-pole, and other furnishings for interior,					284	9	0
	Plumber work of roof,					35	9	6
	A 5 feet achromatic telescope, with stand, &c., for Signal Tower,					35	10	0
	Cost of a code of signals, flags, return books, and other furnishings,					11	10	6
										880	18	7
Lights Account.
	Expense of the apparatus required for the lights at the Pier and Signal Tower at Hynish, including fitting up, &c.,					£66	7	0
	Cost of oil and other requisites for upholding these lights,					136	5	8
	Salary of the Lightkeepers, &c.,					131	11	7
										334	4	3
“Skerryvore” Steamer.
	First cost and complete outfit of the steamer Skerryvore,					£5930	0	11
	Alteration on the engines, by raising the shafts, &c.,					423	5	0
	Repairs on the hull and engines, on various occasions, during the progress of the works,					1057	4	2
	Sailing expenses (exclusive of the cost of coals supplied when the steamer was at Hynish), and sundry other minor charges,					5538	10	11	¹⁄₄
										12,949	1	0	¹⁄₄
“Queen” Tender.
	First cost and complete outfit of the “Queen” Tender,					£935	13	3
	Sailing expenses and other charges,					1010	7	9
	Repairs on the hull, rigging, sails, &c.,					77	12	8	¹⁄₄
										2023	13	8	¹⁄₄
Stone Lighters.
	First cost and outfit of four lighters for transporting the Lighthouse blocks, &c., from Hynish to the Skerryvore Rock,					£1666	15	6	¹⁄₂
	Hawsers for towing, mooring-ropes, heaving-lines, &c., used in the course of transporting the stones to the Rock,					249	1	6
	Upholding the lighters in repair, and sundry other charges,					178	9	9	¹⁄₂
	Expense transporting the lighters on various occasions to different places,					58	15	10
	Expense shifting and attending upon the lighters when lying at Leith, and advertising them for sale,					19	9	10	¹⁄₂
										2172	12	6	¹⁄₂
Moorings.
	Cost of the buoys for mooring the vessels belonging to the works in Hynish Bay, and at the Rock, when lying there,					£240	1	3
	Cast-iron mushroom anchors for mooring the buoys,					118	7	4
	Wrought-iron common anchors, grapnels, &c., for mooring the vessels, warping, kedging, &c.,					48	16	1
	Chains and shackles for do., &c.,					354	2	7
	Upholding and keeping in repair the buoys,					4	17	1
										766	4	4
Boats and Attendance.
	Cost of 8 boats, with oars, sails, tackling, &c.,					£207	19	11	¹⁄₂
	Upholding these boats in repair,					28	13	9
	Amount paid for the use of boats and their crews assisting to discharge cargoes from vessels previous to the pier being built,					119	6	0
										355	19	8	¹⁄₂
	Amount paid the owners of hired vessels, as freights of the Lighthouse blocks from the quarries at North Bay, in Mull, to the workyard at Hynish,									1300	14	8	¹⁄₂
Freight and Sailing Expenses.
	Freights and other charges paid the owners of hired vessels, vessels, for the materials which were imported for the use of various departments of the works, exclusive of the Lighthouse blocks from North Bay,									4045	9	7	¹⁄₂
	Wages of labourers, &c., discharging the cargoes from the vessels at the Pier at Hynish, and the wages of workmen quarrying stones for ballast, and putting it on board the vessels,									933	12	10
	Amount paid for travelling expenses, and other charges connected with the transport of the workmen, including the expenses of the Officers, &c., travelling on the business of the works,									1711	11	2
	Cost of the coals supplied to the steamer “Skerryvore,” when plying between the Skerryvore Rock, Hynish, &c., for the household purposes of the different departments of the works, and also for the smith’s forge,									1463	0	7	¹⁄₂
	Cost of the blasting powder used for the purpose of quarrying stones, excavating rocks, &c.									375	14	2	¹⁄₂
Lighthouse Tower.
	Wages of the workmen who were engaged at Skerryvore Rock in building the Tower, and shipping the materials at Hynish for Rock, including the wages of masons, &c., assisting the other tradesmen in the respective departments of their work, after the completion of the building operations,					£2381	11	7
	Cost of the wainscot and other articles for the joinery of the interior of the Lighthouse; the wages of the joiners preparing the wood at Hynish, and fitting it up at the Tower,					1415	5	1
	Green heart and oak for treenails, for securing the lower courses of Lighthouse Tower,					40	10	4
	Plate-glass for windows and borrowed lights in partitions of Tower,					84	7	4
	Lewis bats, hinges, &c., for entrance-door and shutters of Tower, and the locks and other mounting for the interior,					218	15	2
	14 Copper oil-cisterns, a copper-pump, gauging-rods for do.,					276	10	7
	Cast-iron water-tanks and coal-boxes, for interior of Tower,					160	13	9
	A large cooking apparatus for kitchen of Tower, a stove to heat the lower apartments, and cast-iron smoke-tubes for both fire-places,					117	17	7
	A bell-metal railing for balcony,					341	13	1
	A bell-metal ladder from rock to entrance-door of Tower,					194	13	4
	A cast-iron pillar to support floor of light-room,					17	8	7
	A bell-metal lightning-conductor for Tower, and fixtures,					65	13	0
	Cast-iron permanent railway on the Skerryvore Rock, from the landing creek to the Tower; a cast-iron platform near the Tower, and stairs at landing creek,					493	11	8
	A crane erected at the landing creek, for landing materials on the rock,					98	13	2
	A copper flagstaff and ball for the top of the Lighthouse Tower, with bell-metal base, fixtures, pulleys, &c.,					66	10	8
	A brass force-pump, for pumping water up from tanks to kitchen of Lighthouse,					31	17	5
	Premiums paid the seamen who were employed in the shipping department, in lieu of extra time,					454	2	6
	Premiums paid 17 seamen who were employed in the building works at the Rock during the season of 1842, in lieu of extra time,					121	11	0
	Premiums of the landing master at Rock, foreman of masons, &c.,					96	12	0
	Cost of the furniture, bedding, utensils, books, &c., for the Lighthouse Tower,					304	6	10
	Sundry furnishings connected with the building of the Lighthouse Tower,—the wages of workmen quarrying stones at Hynish for Lighthouse Tower, previous to opening quarries at North Bay, and the wages of workmen, and furnishings for the general purposes of the works,					1386	18	5	¹⁄₂
	Cost of three models, in stucco, of different forms of the Lighthouse,					22	4	6
	Cast-iron water-tanks, which were built and secured into recesses of the rock, for the supplying of the rock works,—new water-casks, and their repairs, for taking off water,					17	5	11
	Feu-duty, rent of ground, assessed taxes, &c., for the establishment at Hynish,					143	6	4
										8551	19	10	¹⁄₂
	Cost of the iron and steel which were used for all the departments of the works,									1299	3	5	¹⁄₄
Lightroom and Apparatus.
	Cost of the lantern of cast-iron, with facings of bell-metal, including the cleaning and trimming paths, and bell-metal ladder outside of lantern, and the wages of the contractor’s workmen fitting them up at Skerryvore,					£863	13	6
	Plate-glass for the lantern,					268	4	6
	Copper dome of lantern, including the internal frame of do., drip-pan, copper steps, handles, air-tubes, rain-water pipes, a platform outside of dome for cleaning the vents, with the wages of the contractor’s workmen fitting them up at Skerryvore,					348	16	9
	Machinery of the revolving apparatus, and brass case for do. complete; three machines for pumping the oil for supplying the burner; the expense of the lamps, fountains, &c.; and bell-metal frames for annular lenses, zones, pyramidal lenses, &c., with the wages of the contractor’s workmen fitting up the above apparatus at Skerryvore,					1244	10	6	¹⁄₂
	The charge of Mr François of Paris furnishing eight annular lenses, and two spare do., with eight catadioptric frames of the first order for lower part, and eight pyramidal lenses, with mirrors, for upper part,	£762	0	0
	Expense of transporting the whole apparatus to Leith,	79	7	10
						841	7	10
	Cost of two bells, and one spare do., used during foggy weather,	£107	6	3
	Shafting for do.; bevel wheels, levers, hammers, &c., connecting with the machinery of apparatus,	63	14	11	¹⁄₂
						171	1	2	¹⁄₂
	Eighteen screens for lantern, cased with iron, and brass mounted, with rollers, &c., and the time of workmen fitting them up at Skerryvore,					48	7	6
	Air watch-bells from lightroom to bedrooms and kitchen, time of workmen fitting them up at Skerryvore, and furnishings for the complete working of do.,					34	13	0
	Brass medallion heads and copper tubes for ventilation of lightroom,					8	9	6
	Wood and workmanship making models of the catadioptric zones to a full size, and a brass model of frame for zones to a small scale,					22	1	2
										3851	5	6
Salaries, Agencies, and Office Expenses.
	Salaries of the Engineer, Surveyor, Clerk, and Store-keeper, including expenses of the survey of the rocks and adjoining Islands,					£3262	10	5
	Agency of the Agent at Aberdeen, who made the monthly payments to the workmen’s relatives, and for some time superintending the making of tools; and the agency of the Lighthouse Agent at Greenock transacting business for the works,					294	13	11
	Iron safe, &c., books, and other stationery for the various departments of the works,					99	10	10
										3656	15	2
	Petty disbursements and miscellaneous expenses, made on account of the general purposes of the works,									308	7	9
Lightkeepers’ Houses.
	Wages of workmen, quarrying, dressing, and building the stones of houses at Hynish for light-keepers, building the brick partitions and lining of walls, and the wages of joiners executing the joiner-work,					£1893	6	2
	Timber and other articles used in the joinery of the houses,					462	19	9
	Plumber-work of roof, including the expense of bringing the water into the houses, &c.,					963	18	6
	Bricks for partitions, lining of external walls, &c.,					73	10	0
	Pavement for floors, water-cisterns, &c.,					51	16	0
	Workmanship, executing the plaster-work (the lime being charged in a special account for this article),					38	12	11
	Glass for glazing the windows and fan-lights,					20	12	3
	Locks, hinges, and other mounting for the doors and windows,					101	11	11
	Cans for the chimney heads,					9	16	6
	Furniture, bedding, utensils, &c., supplied for these houses,					299	0	4
										3915	4	4
Pier at Hynish.
	Wages of masons, quarriers, carters, labourers, &c., quarrying, dressing, and building the stones of a pier at Hynish for the landing and shipping of materials,					£2300	17	1	¹⁄₂
	Iron rails for the works of building the pier,					53	10	1
	Timbers for fenders of pier, and other purposes connected with the building of it,					130	19	4
	Cost of a pont for building the pier,					106	8	11
										2591	15	5	¹⁄₂
Dock or Harbour for Tender.
	Wages of workmen, quarrying, dressing, and building stones to form a talus wall and parapet along the south side and round the point of the pier at Hynish; raising the pier one course; excavating rock in the interior of the harbour or dock and along the point of pier; quarrying, dressing, and building the stones of boom-heads and walls of dock; excavating reservoir and forming embankment of do, for scouring sand, &c., from the dock; forming the feeders to reservoir, and the tail-race from reservoir to dock, refreshments to workmen during night and tide works, &c.,					£6676	10	6
	Timber for double set of boom-gates of dock, copper for sheathing their ends, and mounting for booms,					101	2	6
	Timber used in constructing coffer-dams, and for the general purposes of the harbour works,					135	18	0
	Cost of two sluices, and of the machinery, &c., complete for working them,					81	14	0
	Two cast-iron ladders for sides of pier and dock,					13	1	9
	Cost of sea-boots, &c., and keeping them in repair, which were used by the workmen at tide works,					26	12	0
	Cost of silt-pumps, and furnishings of leather, &c., for making others, and keeping them in repair,					9	10	0
	Compensation paid the tenant of the farm of Hynish, for liberty to cut drains for a supply of water for a reservoir,					5	0	0
	Two signal lamps, two torches, turpentine, &c., for signalizing when the tender enters the dock at night,					5	14	8
										7055	3	5
						Total,				£89,817	6	11
Deductions—
	Price of steamer “Skerryvore,” sold,					£1616	0	6
	Do. of sloop “Queen,” sold,					200	0	0
	Do. of 4 Stone Lighters, sold,					225	0	0
	Do. of Horses and Carts, sold,					60	0	0
	Implements sold or afterwards used at other works of the Board,					738	8	10
										2839	9	4
										£86,977	17	7

APPENDIX, No. VII.
EXCERPTS FROM AN ACCOUNT OF EXPERIMENTS UPON THE FORCE OF THE WAVES OF THE ATLANTIC AND GERMAN OCEANS.
By
Thomas Stevenson, F.R.S.E., Civil-Engineer, Edinburgh.
(From the Transactions of the Royal Society of Edinburgh, Vol. XVI.)

The letters (see Plate IV.) D E F D represent a cast-iron cylinder, which is firmly bolted at the projecting flanges G to the rock where the experiments are wanted. This cylinder has a flange at D D. L L is a door, which is opened when the observation is to be read off. A A is of iron, and forms a circular plate or disc, on which the sea impinges. Fastened to the disc are four guide-rods B B B B. These rods pass through a circular plate C C (which is screwed down to the flange D D), and also through holes in the bottom E F. Within the cylinder there is attached to the plate C C a powerful steel spring, to the other or free end of which is fastened the small circular plate K K, which again is secured to the guide-rods B B B B. There are also rings of leather T T, that slide on the guide-rods, and serve as indices for registering how far the rods are pushed through the holes in the bottom; or, in other words, how much the spring has been drawn out or lengthened by the force of the sea acting upon the plate or disc A A. The object of having four leathern rings, where one might have answered the purpose, was merely that they might serve as a check upon each other; and so perfectly did they answer the purpose intended, that in every instance they were found equidistant from the bottom of the cylinder; proving thereby, that after the recoil of the spring, they had all kept their places. The guide-rods are graduated, so as to enable the observer to note exactly the quantity that the spring has yielded.

This instrument, which may, perhaps, be not improperly termed a Marine Dynamometer, is, therefore, a self-registering apparatus which indicates the maximum force of the waves. In the graduation of the instrument, the power of the spring is ascertained by carefully loading the disc with weights, so that when the quantity that the spring has yielded by the action of the sea is known, the pressure due to the area of the disc exposed is known also. The discs employed were from 3 to 9 inches diameter, but generally 6 inches, and the powers of the springs varied from 10 lb. to about 50 lb. for every ¹⁄₈ inch of elongation. Their respective effects were afterwards reduced to a value per square foot. The instrument was generally placed so as to be immersed at about three-fourths tide, and in such situations as would afford a considerable depth of water. It is not desirable to have the instrument placed at a much lower level, as it has not unfrequently happened during a gale, that for days together no one could approach it to read off the result and readjust the indices to zero. It must, however, at the same time be remarked, that it is in most situations almost impossible to receive the force unimpaired, as the waves are more or less broken by hidden rocks or shoal ground before they reach the instrument.

In connection with the apparatus above described, a graduated pole was erected on an outlying sunken rock, for the purpose of ascertaining the height of the waves; but the observations were not of so satisfactory a nature as could have been desired, and the poles soon worked loose from their attachments, and disappeared.

With the instrument which has been explained, I entered upon the following train of observations:—

In 1842 several observations were made on the waves of the Irish Sea at the island of Little Ross, lying off the Bay of Kirkcudbright. Since April 1843 till now, continued observations have been made on the Atlantic at the Skerryvore and neighbouring rocks lying off the island of Tyree, Argyllshire; and in 1844 a series of observations was begun on the German Ocean at the Bell Rock. It will be seen, that in selecting these localities a varied exposure has been embraced, comprising the comparatively sheltered Irish Sea, the more exposed eastern shore of Scotland, and the wild Rocks of Skerryvore, which are open to the full fury of the Atlantic, the far distant shores of North America being the nearest land on the west.

Referring for more full information to the tables of experiments which are given at the end of this paper, it will be sufficient in this place to state generally the following as the results obtained.

In the Atlantic Ocean, according to the observations made at the Skerryvore rocks, the average of results for five of the summer months during the years 1843 and 1844, is 611 lb. per square foot. The average results for six of the winter months (1843 and 1844), is 2086 lb. per square foot, or thrice as great as in the summer months.

The greatest result yet obtained at Skerryvore was during the heavy westerly gale of 29th March 1845, when a pressure of 6083 lb. per square foot was registered. The next highest is 5323 lb.

In the German Ocean, according to the observations made at the Bell Rock, the greatest result yet obtained is 3013 lb. per square foot.

It thus appears, that the greatest effect of the sea, which has been observed, is that of the Atlantic at Skerryvore, which is nearly equal to three tons per square foot.

These experiments, amounting to 267 in number, and on the Atlantic alone, extending over 23 months continuously, are not intended to prove anything farther than the simple fact, that the sea has been known to exert a force equivalent to a pressure of three tons per square foot, however much more.

It is proper, however, to observe, that there may be some objection to referring the action of the sea to a statical value. Although the instrument might perhaps be made capable of giving a dynamical result, it was considered unnecessary, in these preliminary experiments, to do anything more than represent the maximum pressure registered by the spring, because the effects of the waves may, from supposing them to have continuity of action, be perhaps regarded as similar to a statical pressure, rather than to the impact of a hard body. The near coincidence, or indeed almost perfect agreement of the results of the experiments made with different instruments, goes far to shew that the waves act in very much the same manner as a pressure, although both pressure and impact must obviously enter into their effect. In the experiments, begun February 1844, and given at the end of the paper, the three instruments had not only different areas of discs, but very different powers of springs, and yet the results were almost identical. Now, the same force, supposing the waves to act like the impact of a hard body, would, in the Marine Dynamometer, have assumed very different statical values, according to the spaces in which that force was expended or developed; so that with the same force of impact, the indication of a weak spring would be less than that of a stronger.

In future experiments it may be interesting, however, to test the springs dynamically, by means of the impact of a heavy body dropped from a given height upon the plate or disc of the instrument. In some experiments lately made in this way, by dropping a cannon-ball upon the disc, it appeared, that, within the limits of the experiments, there was for each individual spring a ratio between the value registered by the leathern index and the calculated momentum of the impinging body. These ratios were, of course, found to vary in springs of different power, and to be constant only for springs of the same power. Did the waves, therefore, act by a sudden finite impact, like the cannon-ball employed in this instance, we could scarcely have found such harmony between the results of instruments with different springs, as the experiments alluded to afford. At the same time, the result cannot, perhaps, be in strictness considered correct; but, from the elongation of the spring being very small, the results may be regarded as practically correct,—the more so when we find so remarkable a coincidence of results as that alluded to.

Experiments.—With reference to the following experiments I have only to observe, that those which were made at Little Ross, upon the Irish Sea, cannot, from the unusual fineness of the weather at the time, be regarded as affording a true value of the effects of a hard gale in these seas. Of the others it is to be noticed, that where two or three instruments were for some time employed as a check upon each other, and only one or two readings are given, the want has occurred either from the instruments being under repair, or being difficult of access in stormy weather, or during neap tides. It often happened also, in consequence of the springs proving too weak, when new ones had to be made, or the area of the disc reduced. Registers of the state of the weather, apparent height of spray, &c., were generally kept; but it was not considered necessary to complicate the Tables by inserting these, excepting in one or two instances.

Dates.		lbs. to a Square Foot.
Observations at Little Ross.
1842.
April	25		15
April	28		51
June	1		36
	4		81·5
	20		86·5
	24		840·0
	25		458·0
July	25		380·0
Aug.	2		570·0
	5		665·0
	6		380·0
	9		380·0
The Observations at the Skerryvore Rock, and the neighbouring Island of Tyree, distant 13 miles from the Skerryvore, are as follows:—
1843.
April	24		455
April	25		707
May	7		243
	11		182
	12		243
	16		364
	20	-	495
	20	-	476
June	3		182
	4		519
	7		428
	8		855
	9		173
July	2		476
	3	-	723
	3	-	866
	30		433
Aug.	9		346
	22		723
	30		389
Sept.	5		866
Sept.	21		952
Oct.	5		1535
Oct.	6		1606
Nov.	18		1711
	19		1497
	27		1497
	29		2353
Dec.	5		2674
	8	-	3421
	8	-	At least
	14		2460
	26		1947
In January, two instruments were placed beside each other, but not set parallel. These instruments had springs of different power, the one being about double that of the other, and one had a disc of 3 inches diameter, the other 6 inches.
1844.
Jan.	6		962
			928
	7		2353
			357
	9		1925
			1000
	10		826
			1000
Both instruments set parallel.
	16		424
			427
Another instrument was placed beside them, but the two marked thus* were found to be too weak, as the leathers were found flattened, and one of the instruments was broken, and was not repaired till the 15th February.
	28		3422	*
			2285	*
			3313
Feb.	2		429
			457
	3		429
			457
	13		214
			228
	15		321
			280
			321
	16		428
			402
			343
	24		1284
			1364
			685
	26		2032
			2068
			399
	27		321
			321
			342
March	4		3316
			3369
			3427
	7		1069
			963
			913
	10		1925
			1925
			1713
	11		535
			481
			456
	12		3316
			4011
			2970
	13		1142
			1283
			1283
April	10		457
			428
			481
	11		800
	12		343
			321
	14		571
			535
	16		571
			642
			481
	17		800
			856
			862
	18		571
			481
	19		800
			535
			481
	22		913
			482
			962
	24		1942
			1604
			1370
	25		1283
			343
			321
	27		457
			481
		-	Night	800
		-	tide	800
			642
	30		229
			241
May	15		343
May	14		481
June	6		571
June	15		1828
July	11		1028
	13		457
	18		914
	23		1532
	25		571
	26		971
	27		457
	28		1142
	29		286
	30		914
	31		1028
Aug.	1		571
	7		914
	13		914
	14		914
	21		800
	30		1713
Sept.	12		1028
	14		914
	20		457
	23		1142
	25		685
	30		1599
Oct.	2		2399
	3		1485
	4		1828
	11		3427	[88]
	14		1599
	19		1599
	20		2513
	22		800
	24		1827
	28		1485
	29		457
Nov.	2		1942
	10		1028
	14		1257
	15		2056
	16		2056
	22		2627
	23		3427
	27		3199
	28		4112
Dec.	7		1369
	9		2738
	10		1825
	13		1925
	14		1027
	15		1764

[88] On this occasion, 14 stones were slightly moved, and 14 scattered, all of which had been built into the round-head or end of Hynish Pier, which was still in an unfinished state, and a Dynamometer which was attached to the Pier, registered on this occasion 2557 lb. These stones weighed from 1 to 1¹⁄₂ tons, and exposed, when built into the wall, about two square feet of surface. The stone to which the instrument was fixed was turned upside down, although it weighed about 1¹⁄₄ ton = 2800 lb.

A more exposed point of the Skerryvore Rock was at this time chosen for experiment; and with the view of ascertaining the effect of the waves at different heights upon the rock, two instruments were fixed, the one (No. I.) several feet lower, and about 40 feet seaward of the other (No. II.). It was observed, that about half-flood the force of the waves was a good deal expended before they reached the place where No. I. was placed, from there being so little water on the rocks outside; whereas when the tide was higher, the waves were, from the greater depth of water, not so much broken when they reached No. II. The results of the Marine Dynamometer shew generally about twice the force at No. II. as at No. I.; a result which shews how important it would be to ascertain the relative forces of the waves at different levels upon our breakwaters and other seaworks.

Date.		Remarks.	No. of Instru- ment.	Pressure in lbs. per Square Foot.
1845.
Jan.	7	Heavy sea.	I.	1714
		...	II.	4182
	12	Very heavy swell.	I.	2856
		...	II.	5032
	16	Heavy ground swell.	I.	2856
		...	II.	4752
	22	A good deal of sea.	I.	2856
		...	II.	5323
	28	Heavy ground swell.	I.	2627
		...	II.	4562
Feb.	5	Fresh gales.	I.	856
		...	II.	3042
	21	...	I.	1827
		...	II.	3422
	24	Fresh breezes.	I.	1256
		...	II.	3802
March	9	Ground swell.	I.	1256
		Waves supposed about 10 feet high.	II.	3041
	11	Short sea.	I.	1028
	24	Heavy sea.	I.	2281
		Waves supposed about 20 feet high.	II.	4562
	26	Swell.	I.	1256
		Waves about 6 feet high.	II.	3041
	29	Strong gale, with heavy sea, the highest waves supposed 20 feet high, and the spray rose about 70 feet.	I.	2856
		...	II.	6083

Register of Observations on the force of the Sea, made at the Bell Rock, German Ocean.

Dates.		lbs. to a Square Foot.
1844.
Sept.	15	853
Sept.	20	2260
Oct.	9	3013
	...	2562
	26	1142
	27	958
Nov.	12	1680
Nov.	13	1920
Dec.	13	1560
Dec.	26	1439
1845.
Jan.	7	1559
	10	1439
	11	1439
	15	1559
	25	959
	26	719
	27	1199
	30	2879
	31	1559
Feb.	6	2999
	24	1199
	25	959
	27	839
	28	1319
March	4	959
	7	1079
	11	1919
	20	2519
	21	2759
	24	1319
	25	959
	28	599
	30	1079

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