M..M..IK XXX.] ON lU'KMNti QLA88B9 AND MIKKnUv j j- 



trough \va> not used. Though tlie sun's r.i\> 

 wi-re not brilliant, the chloride at once melted, forming a 

 reddish -looking liquid. It was kept in that condition 

 all day. When cool it proved to be in the state of 

 horn-silver, easily cut by a knife. When the rays first 

 touched it a fume was disengaged, due* probably to the 

 escape of vapor of water. It seems, therefore, that this 

 substance when perfectly dry is not decomposable by- 

 sunlight, though so sensitive at common temperatures 

 when moist. 



In Fig. 95, a is the platinum crucible ; &, the place of the 

 material experimented upon, re- 

 ceiving at the focus the converg- 

 ing rays, c. 



I must refer to the original 

 Memoir for the detail of numer- 

 ous experiments on many metal- 

 lic compounds, the general re- 

 sult of these being that, no mat- 



ter how brilliant a ray may be, it cannot carry a decom- 

 position farther than a feeble one acting for a corre- 

 sponding longer period of time could do. Compounds 

 that can resist the force of an ordinary ray cannot be 

 broken down by the intense illumination of the focal 

 point of a burning -lens. That instrument cannot do 

 what the voltaic pile has done effect decompositions 

 which had never been effected before. 



To reduce the disturbing effect of heat as far as pos- 

 sible, and give every advantage to the condensed lumi- 

 nous focus, I received the cone of rays coining from the 

 twelve -inch burning -lens on a glass globe (Fig. 90) six 

 inches in diameter, filled with water. This increased 

 the converging of the rays, and brought them more 

 quickly to a focus. Then through the neck of the globe 

 was introduced to the focus, in a matrass, spoon, or other 



