On the functions of the colouring matter of the skin in the dark races of mankind / by Robert Mortimer Glover.
- Robert Mortimer Glover
- Date:
- [1840?]
Licence: Public Domain Mark
Credit: On the functions of the colouring matter of the skin in the dark races of mankind / by Robert Mortimer Glover. Source: Wellcome Collection.
Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.
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![rence to the original paper will convince the reader that this assumption is established without sufficient data. Most stress has been laid by Sir Everard, and those who have adopted his views, on the seventh experiment. We are told that, on the 9th of September, at 11 A, M., thermometer 90° in the sun, the concentrated rays applied to a piece of black ker- seymere wrapped round the arm, gave no real pain, as it is ex- pressed, during 15 minutes ; and at the end of that time left no appearance on the arm ; whereas, when white kerseymere was substituted, during the same time, and the concentration we are led to suppose being the same, the heat of a thermo- meter in the sun only 86°, yet blisters were formed. From this experiment, taken along with those preceding, it is sup- posed to be fully proved that although black surfaces rise to a higher temperatui*e than white under the sun's rays, yet they scorch the surface of the body less; the scorching effect de- pending on a union of the rays of heat with those of light, the latter being supposed, by way of explanation, to be excluded by the black surface. First, I shall state my repetition of the experiment, and then attend to Sir Everard's explanation of his supposed fact. I have attempted to ascertain the rise which the absorption of heat by black and white cloths respectively gives to the thermometer; to compare this observation with the effects of the same cloths under the sun's rays upon the body, and with the effect of the sun's rays on the naked skin. When the ther- mometer stands at about 80° in the sun, the solar rays con- centrated on white cloth over the ball of a thermometer, to a space of an inch and a half in diameter by a burning-glass, caused a rise of the thermometer to 125° in a quarter of an hour. When black cloth was substituted the rise during the same period was to 172. In five minutes, with the white, the rise was to ] 08°, with the black to 140°; and in some experi- ments in a proportion nearer that given by the longer period. When the black and white cloths were applied to the skin : at the same temperature, and with the same degree of concen- ' tration, as already mentioned, the black cloth generally caused i intense pain in the course of a few minutes, and on being al- lowed to remain for five or at mo. t seven minntee, produced](https://iiif.wellcomecollection.org/image/b21470054_0007.jp2/full/800%2C/0/default.jpg)
