IN THE LAST HALF-CENTURY. Ill 



ence. In the hands of the astronomer and 

 the meteorologist, it has yielded means 

 of registering terrestrial, solar, planetary, 

 aud stellar phenomena, independent of 

 the sources of error attendant on ordinary 

 observation ; in the hands of the physi- 

 cist, not only does it record spectroscopic 

 phenomena with unsurpassable ease and 

 precision, but it has revealed the exist- 

 ence of rays having powerful chemical 

 energy, iW beyond the visible limits of 

 either end of the spectrum ; while, to the 

 naturalist, it furnishes the means by 

 which the forms of many highly compli- 

 cated objects may be represented, without 

 that possibility of error which is inherent 

 in the work of the draughtsman. In fact, 

 in many cases, the stern impartiality of 

 photography is an objection to its em- 

 ployment : it makes no distinction be- 

 tween the important and the unimpor- 

 tant; and hence photographs of dissec- 

 tions, for example, are rarely so useful 



