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III. Remarks on Microscopic Chemistry. By the Rev. Edward 

 Craig, M.A., F.R.S.E.* 



¥T has been suggested to me that a short notice of some 

 -'- modes which I have adopted for examining under the mi- 

 croscope the phasnomena attendant on chemical action, might 

 tend in some degree to facilitate the researches of other and 

 abler men in this department of inquiry. Not that the subject 

 can be regarded as altogether new : after the lengthened and 

 accurate observations of Leeuwenhoeck, Hooke, and others, 

 on minute substances, it is impossible that the particular point 

 to which my attention has been turned can altogether have 

 escaped notice ; yet the microscopic investigation of chemical 

 agents in a state of reaction has certainly not occupied atten- 

 tion as much as it seems to merit. 



M. Raspail published recently in Paris, a work which he 

 entitles Noiivel Systeme de Chimie orgaiiique, fondc sur des 

 methodes nouvelles d' Observation. I have met with this work 

 since the origination of my own modes of observation ; and 

 it fully justifies the idea, that notwithstanding the long time 

 that the microscope has been in use, it has never been effec- 

 tively applied to the object in consideration. 



M. Raspail's work is a detailed account of the examination 

 of organic structures ; and the mode of observation for this pur- 

 pose on which he lays the most stress, as having a claim to 

 novelty, is the microscopic investigation of the visible effect 

 produced on such structures by chemical agents, " I carry," 

 he says, " the laboratory of the chemist on to the port-objects 

 of the microscope." His very elaborate and valuable treatise 

 closes with a note to the appendix, vindicating the novelty and 

 originality of his modes of observation. 



My own observations, conducted by one so much a novice 

 in matters of scientific inquiry, are in themselves necessarily 

 unimportant; they have, however, been carried on inde- 

 pendently of any knowledge of M. Raspail's work; and they 

 have a different object, in as much as M. Raspail confined 

 himself to means for observing a particular class of phseno- 

 mena. The particular object to which my attention was turned 

 was the adoption of arrangements by which chemical action 

 generally in the minutest visible quantities of substances might 

 be examined. 



Some months ago I was led by the statement of Dr. Brown, 

 the eminent scientific botanist, to examine the motion of small 

 molecules of matter floating in water, and excluded from the 



• Read before the Royal Society of Edinbiirgli in December 1834; and 

 now communicated by the Author. 



