ON THK PHYSICAL VIKW OF NAILl;K. 



lol 



portion as experiiULUlul science has tak(Mi the place of 

 that purely mathematical treatment wliich ul)tained at 

 the beginning of the century, notably in the Continental 

 schools, and whirh thought it could exhaust the infinite 

 variety of natural phenomena by a few easily defined 

 properties measured by constants. The narrowness of 

 this view has been gradually overcome by the inlluenco 

 of the great experimental philosophers in this country, 

 and the indepemlent development of chemical research 

 abroad. IJeside Faraday must be especially named Thomas 

 Graham ^ and Thomas Andrews, whose original experi- 89, 



Gnham and 



ments did so much to extend and deepen our knowledge Andrews, 

 of the less obvious properties of matter. Graham car- 

 ried on, between 1825 and 1850, extensive experiments 

 on the diffusion of liquids and gases, on absorption, and 

 on the phenomena of osmosis or gradual filtering of sub- 

 stances through porous partitions, showing how in liquids 

 motion and pressure exist similar to that which is now 



1 Thomas Graham (1804 - 69), 

 for many years professor at Uni- 

 versity College, London, then 

 Master of the Mint, cultivated the 

 unexplored regions of physics and 

 chemistry in an original si)irit and 

 yet with very himple apparatus, 

 some of which is still used under 

 his name. His ingenious labours 

 attracted the attention of Liebig, 

 through whose intluence was brought 

 about the translation of ' The Ele- 

 ments of Chemistry ' into Ger- 

 man by Otto. This work in its 

 subsequent enlarged editions has 

 formed for sixty years, next to 

 Gmelin's ' Handbook,' a corner- 

 stone of chemical literature in 

 Germany, where Graham's name 

 ia a hou.sehold word. The dia- 

 coveries of Graham on the move- 



VOL. n. 



ment and " miscibility " of gases 

 led to the well-known law, " that 

 the diffusion rate of gases is in- 

 versely as the square root of their 

 density." From ga.ses he advanced 

 to the more comi)licated study of 

 liquids, divided bodies into two 

 classes, "crystalloids" and "col- 

 loids," studied the " transpiration " 

 of gases tlirough fine tul>c.s, and 

 their "osmosis" or gradual filtering 

 through porous (and many ap- 

 parently noil - porous) partitions. 

 In many directions he anticipated 

 later discoveries and collecte«l in- 

 valuable materials for subsecjuent 

 theories. Inter alia, he establislicd 

 the existence of '" alcohoLites," 

 compounds analogous to " iiydrates," 

 and niaiiiUiined the metallic nature 

 of hydrogen. 



