1 60 EXPERIMENTS and OB SER VA TIONS 



THE iflue of experiments, made with this view, feemed to 

 offer an alternative, according to which any farther refearches 

 might be conducted to greater advantage : For as yet, I was 

 uncertain, whether fo anomalous a phenomenon originated 

 from fome property of fnow in relation to the air at the time 

 of giving out its hoar-froft, or whether it depended upon the 

 mere feparation of hoar-froft from the air, by that affinity 

 which bodies in general have to hoar-froft. I accordingly be- 

 gan with the following trial : 



JANUARY 24. 1784. 



THIS night, the heavens being very ferene, and the wind 

 coming gently from the eaft, and every thing without doors 

 greedily attracting hoar froft, the fnow-fcale, formerly men- 

 tioned, was expofed upon a long frame, four feet high. To- 

 wards the other end of the frame, T placed a circular board, of 

 the fame diameter, covered with fine flinty fand, free of duft, 

 much like that made ufe of for fand-glafles. A thermometer 

 was laid upon the fnow in the fcale, and another upon the 

 fand, with their naked balls, within a few inches of the moft 

 leeward fide. A foot to windward, and at an equal diftance 

 from the fcale and board, and even with their furface, another 

 thermometer was expofed to the air. After waiting a confi- 

 derable time, with fome curiofity, to know the iflue of this ex- 

 periment, I returned to view the apparatus at half an hour 

 after ten o'clock, when, at once, I found reafon entirely to re- 

 linquifli all my former conjectures, by which, I thought, I 

 might poflibly account for the phenomenon, by fome proper- 

 ties peculiar to fnow : For now I faw diftinftly, that the excefs 

 of cold was moft remarkable at the furface of the fand. At 

 this time, the thermometer expofed to the air, which afterwards 

 fweeped the apparatus, pointed to +14, whilft the one upon 

 the fnow pointed to + 10, and that upon the fand to + 8. I 

 continued to obferve till half an hour after one in the morning ; 



and 



