Appendix I
Most people are very much interested in how hot it gets in such tropics as we traversed. Unfortunately it is very difficult to tell them. Temperature tables have very little to do with the matter, for humidity varies greatly. On the Serengetti at lower reaches of the Guaso Nyero I have seen it above 110 degrees. It was hot, to be sure, but not exhaustingly so. On the other hand, at 90 or 95 degrees the low coast belt I have had the sweat run from me literally in streams; so that a muddy spot formed wherever I stood still. In the highlands, moreover, the nights were often extremely cold. I have recorded night temperatures as low as 40 at 7000 feet of elevation; and noon temperatures as low 65.
Of more importance than the actual or sensible temperature of the air is the power of the sun’s rays. At all times of year this is practically constant; for the orb merely swings a few degrees north and south of the equator, and the extreme difference in time between its risings or settings is not more than twenty minutes. This power is also practically constant whatever the temperature of the air and is dangerous even on a cloudy day, when the heat waves are effectually screened off, but when the actinic rays are as active as ever. For this reason the protection of helmet and spine pad should never be omitted, no matter what the condition of the weather, between nine o’clock and four. A very brief exposure is likely to prove fatal. It should be added that some people stand these actinic rays better than others.
Such being the case, mere temperature tables could have little interest to the general reader. I append a few statistics, selected from many, and illustrative of the different conditions.
| Locality. Elevation | 6am | noon | 8pm | Apparent conditions |
| Coast —- | 80 | 90 | 76 | Very hot and sticky |
| Isiola River 2900 | 65 | 94 | 84 | Hot but not exhausting |
| Tans River 3350 | 68 | 98 | 79 | Hot but not exhausting |
| Near Meru 5450 | 62 | 80 | 70 | Very pleasant |
| Serengetti Plains 2200 | 78 | 106 | 86 | Hot and humid |
| Narossara River 5450 | 54 | 89 | 69 | Very pleasant |
| Narossara Mts. 7400 | 42 | 80 | 50 | Chilly |
| Narossara Mts. 6450 | 40 | 62 | 52 | Cold |