750 LECTURE LX. 



of the variation for every part of the globe ; but their success has been very 

 much limited. 



The science of electricity was diligently cultivated in the middle of the 

 last century by Stephen Gray, Dufay, Winkler, Nollet, Musschenbroek, and 

 .Franklin. As early as 1735 it was remarked by Gray, that "the electric fire 

 seemed to be of the sanie nature as lightning," and their identity was after- 

 wards more strongly asserted by Winkler, and experimentally demonstrated by 

 Franklin. The shock of a charged jar was first discovered by Kleist, in 1745; 

 and the experiment was repeated by Lallamand and Musschenbroek, who de- 

 scribed its disagreeable effects on the sensations with an exaggeration not the 

 most philosophical. The theory of the nature of the charge was the second 

 gceat improvement made by Dr. Franklin in this science. 



The introduction of the Linnean system of botany and zoology is to be 

 considered as bringing near to perfection the logic and phraseology of natu- 

 ral history; nor has its celebrated author wholly neglected the philosophy of 

 the science. The number and the diligence of his successors have already 

 furnished to the different departments of natural history a much ampler store 

 of observations than could easily have been expected from the short time 

 which their labours have occupied. Buffon had merit of a different kind, 

 and though his fancy was too little regulated by mathematical accuracy, the 

 elegance of his writings have made their subjects highly interesting to the 

 general reader. Among other modern naturalists of great respectability, Spal- 

 lanzani, Daubenton, Degeer, Geoffrey, Pennant, the Jussieus, Lacepede and 

 Haiiy, have particularly distinguished themselves by the importance of theit 

 discoveries, and the accuracy of their descriptions. 



The absorption of heat, during the conversion of ice into water, appears to 

 have been separately observed by Deluc, Black, and Wilke, about the year 

 1755, On this experiment Dr. Black principally founded his doctrine of la- 

 tent heat, supposed to 'be retained in chemical combination by the particles 

 of fluids. Dr. Irvine and Dr. Crawford explained the circumstances some- 

 what, differently, by the theory of a change of capacity for heat only. Berg- 

 njann, Lavoisier, Laplace, Eifwan, Seguin, and many other philosophers have 



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