An Essay on the Degi'ee of IVarmth of coloured Bays. 413 



be surprised at the variations I have experienced, although they 

 are considerable. 



In the mouth of July of 1776, the thermometer having only 

 varied from IS" to 20' during the course of the experiments : 

 The violet was 3 Green 31 Red 38 



4| 39 40 



3| 271 37 



5 30 36| 



Violet 6 Yellow orange 49 Green 33 Red 40 



7 52 SU 39| 

 6f 48 . 36' 45 



8 64 48 60 



In the month of August Reaumur's thermometer rose from 

 1 9° to 23", during the following observations : 



Violet 7 Orange 60 Green 43 Red 5G 



Violet 6 yellow orange 62 green 39 red 55 

 Violet 7 orange 38 green 45 red 64 



5 51 39 48 



In the month of September, I used a thermometer of the con- 

 struction represented by fig. 5, Plate VIII. on which the exterior 

 air had no influence ; the bubble of air was always similarly ex- 

 posed, for two minutes, to the action of the coloured rays, as in 

 the preceding experiments; but the sensibility of the thermo- 

 meter no longer contiimed to be so great. 



In the month of September, Reaumur's thermometer varied 

 from 19° to 1(5' in the course of the observation.".: 

 Violet 2 Yellow orange 18 

 2 orange 17 



2-^ orange 22 



2J^ 20 



6* 

 4 



H 



71 



' 4 



3 



5 



6 orange 49 



7 yello\\' orange 52 

 6^- orange 48 

 6 50 



It follows from all these experiments, and notwithstanding the 

 great differences which are to be found amongst them, and how- 

 ever attentive I was in making them ; first, that the ratio of the 

 warmth of clear red to the most lively violet, is nearly as 8 to 1 , 



for 



