•J^^t TWO INTERSECTrNG RAINBOWS. 



yns -y^yths of an inch. The thermometer was adapted to Fab^ 

 jeniieii's fcale, and the refults of three experiments are exhi- 

 bited in tiie following table : 



Number of i Time of Tlierrn, 



Blatts. I blowing* 



Ejp. I. - 425 j 6 minutes. 



2. - 222 3 



3» - 217 3 



rofc. 



3.75 

 3.7 



The current of air was direded againft the bulb of the 

 thermometer. The diflance of the pipe out of which the air 

 iilued, was half an inch from the bulb. The experiments 

 were repeated with every caution poflible for twelve times, 

 and always with the fame refults. 



Mr. Dalton obferved (Philof. Journal, III. 160), that the 

 thermometer fell on exhaufting the vefTel in which it was 

 placed, and rofe again on re-admitting the air. It is probable 

 that the rifing of the thermometer in my experiments may be 

 referred to tlie fame caufe, viz. the greater capacity of a va» 

 cuum for caloric than atmofpheric air. 



XVII, 



^n Account of two interft'ftbv^ Rainbows, feen at Dimglafs 

 in Eafi Lothian in July luji, was communicated by Frofejfor 

 Plavfair *. 



Large rainbow 1 JlT Dunglafs, where I happened to be in the beginning 

 ■where ^the fu:j of July laft, 1799, our attention was called one evening, a 

 "" little before funfet, to a very large and beautiful rainbow, 

 formed on a cloud which hung over the fea, and from which a 

 lliower was falling at a confiderable diftance to the S. E. The 

 fufl was about 2° high, fo that (he arch was not much lefs than 

 Anoi her inter- ^ femicircle, with its highefi point elevated about 40''. At 

 i'e<3ins bow, {\)q point where the northern extremity of this arch touched the 

 horizon, another arch feemed alfo to fpring from the fea, di- 

 verging from the former al an angle of 3^ or 4"^, on the fide 

 tov\ard the fun. 



* Edin. Tra«r. 1805. Hiftory, p. S. 



This 



over the fea. 



