336 Dr. Seebeck on the unequal Evolution 



noticed that the temperature of the room had increased by 5\ 

 lines during the experiment between the two extremes. 



Exp. 3. — With the same prism, No. 1. The thermoscope 

 six feet distant. Only made concerning the excitation of heat 

 in and below the red. The second thermoscope stands near 

 the spectrum at the distance of four inches. 



1st Thermoscope, 2d Thennoscope, 

 in the Spectrum. near it. 



Station at the beginning of the ex- ") ^„ ^,„ ^„ ^,„ 



periments / 



Four inches below the red ... 7 Of 54 



Three inches and a half ditto . . 7 1| 



Three inches ditto 7 2^ 5 4 



Two inches and a half ditto . . 7 3| 



Two inches ditto 7 6| ^ H 



One inch and a half ditto ... 8 1 1 



One inch ditto ....... 8 10^ 5 3| 



Half an inch ditto 10 8^ 



Close under the red 13 9 5 3| 



In the red 14 3 5 3j 



This experiment, which was made under the most favourable 

 circumstances on the 19th of September 1807, may be consi- 

 dered as being decisive ; and it not only serves to confirm the 

 results of the two preceding ones, but also shows that the ef- 

 fect on the thermoscope extends, within the distance men- 

 tioned, to four inches beyond the limits of the red, and the 

 entire spectrum. 



It will be useless to mention a greater number of experi- 

 ments concerning the differences of tempei'ature of the yellow 

 and red half of the rays from this prism ; I will only observe, 

 that all which were made under favourable circumstances gave 

 the same result. 



I shall now give a few experiments on the elevation of tem- 

 perature beyond the blue and violet half, of which the second 

 experiment has already given us an instance. 



Exp. 4. — The prism. No. 1, at the same distance from the 

 thermoscope. 



Station of the thermometer by the side of the") „ ,„ 



spectrum one inch and a half above the violet J 

 One inch and a half above the violet itself, 1 4 i a 



remained / 



Half an inch above the violet 4 lOi 



Close above ditto 5 



Halfin ditto 5 U 



A litde deeper in ditto 5 5h 



In full ditto 6 0" 



Outside the spectrum 5 Of 



Exp. 5 



