REF 



REF 



mirror, was the cause of the rise of the 

 thermometer. He made another experi- 

 ment, substituting boiling water in a giass 

 vessel in place of the iron ball ; and when 

 the apparatus was adjusted, and a screen 

 of silk which had been placed between 

 the two mirrors removed, the thermometer 

 rose 3 ; namely, from 47 to 50. The 

 experiments were varied by removing 1 the 

 tin mirrors to the distance of 90 inches 

 from each other. The glass vessel with 

 boiling water was placed in one focus, 

 and a sensible thermometer in the other. 

 In the middle space between the mirrors, 

 there was suspended a common glass 

 mirror, so that either side could be turn- 

 ed towards the glass vessel. When the 

 polished side of this mirror was turned to- 

 wards the glass vessel, the thermometer 

 rose only live-tenths of a degree ; but 

 when the other side, which was darkened, 

 was turned towards the glass vessel, the 

 thermometer rose 3 5'. And in another 

 experiment performed, in the same way, 

 the thermometer rose 3 when the polish- 

 ed side of the mirror was turned to the 

 glass vessel, and 9 when the other side 

 was turned. These experiments show 

 clearly, that the rays of caloric are re- 

 flected from polished surfaces, as well as 

 the rays of light. Transparent bodies 

 have the power of refracting the rays of 

 caloric as well as those of light. They 

 differ also in their refrangibility. So far 

 as experiment goes, the most of the rays 

 of caloric are less refrangible than the 

 red rays of light. The experiments of 

 Dr. Hei schel show, that the rays of ca- 

 loric, from hot or burning bodies, as hot 

 iron, hot water, fires and candles, are re- 

 frangible, as well as the rays of caloric 

 which are emitted by the sun. Whether 

 all transparent bodies have the power of 

 transmitting these rays, or what is the 

 difference in the refractive power of these 

 bodies, is not yet known. 



The light which proceeds from the sun 

 seems to be composed of three distinct 

 substances. Scheele discovered, that a 

 glass mirror held before the fire reflect- 

 ed the rays ot light, but not the rays of 

 caloric ; but when a metallic mirror was 

 placed in the same situation, both heat 

 and light were reflected. The mirror of 

 glass became hot in a short time, but no 

 change of temperature took place on the 

 metallic mirror. This experiment shows 

 that the glass mirror absorbed the rays 

 of caloric, and reflected those of light; 

 while the metallic mirror, suffering no 

 change of temperature, reflected both. 

 And if a plate of glass be held before a 



burning body, the rays of light are not 

 sensibly interrupted, but the rays of ca- 

 loric are intercepted ; for no sensible heat 

 is observed on the opposite side of the 

 glass : but when the glass has reached a 

 proper degree of temperature, the rays of 

 caloric are transmitted with the same fa- 

 cility as those of light. And thus the 

 rays of light and caloric may be separa- 

 ted. But the curious experiments of Dr. 

 Herschel have clearly proved, that the 

 invisible rays which are emitted by the 

 sun, have the greatest heating power. 

 In these experiments, the different co- 

 loured rays were thrown on the bulb of a 

 very delicate thermometer, and their 

 heating power was observed. The heat- 

 ing power of the violet, green, and red 

 rays, were found to be to each other as 

 the following numbers : 



Violet 16.0 



Green 22.4 



Red 55.0 



The heating power of the most refraiv 

 gible rays was least, and this power in- 

 creases as the refrangibiiily diminishes. 

 The red ray, therefore, has the greatest 

 heating power, and the violet, which is 

 the most refrangible, the least. The il- 

 luminating power, it has been already ob- 

 served, is greatest in the middle of the 

 spectrum, and it diminishes towards both 

 extremities ; but the heating power, 

 which is least at the violet end, increases 

 from that to the red extremity ; and when 

 the thermometer was placed beyond the 

 limit of the red ray, it rose still higher 

 than in the red ray, which has the greatest 

 heating power in the spectrum. 'J he heat- 

 ing power of these invisible rays was great- 

 est at the distance of half an inch beyond 

 the red ray, but it was sensible at the dis- 

 tance of one inch and a half. See OPTICS, 

 REFORMATION, in church history, 

 is that amazing change in the religion 

 and politics of a great part of Europe, 

 which began to take place in the early 

 part of the sixteenth century. An event 

 of such magnitude, with which the pro- 

 gress of the arts and universal learning is 

 so intimately connected, demands a more 

 enlarged and detailed account than the 

 prescribed limits of our work will admit. 

 It would, nevertheless, be highly impro- 

 per wholly to omit the notice of so very 

 important an era in the history of Europe." 

 At a time when the peace and harmo- 

 ny of the Romish Church seemed fully 

 established, and when the authority of the 

 Holy See had just received a most signal 

 triumph by the labours of the Council of 



