14? The Rev. E. Craig's Rejnarks on Microscopic Chemistry. 



therefore, should be of such a focus as to allow of its being 

 above the reach of the vapours that arise, and that would 

 otherwise condense on it and obstruct the view. Some little 

 tact and experience also are required to manage the wires of 

 the battery, because under the compound microscope they 

 appear reversed. I will give an instance or two. When the 

 copper wires were put into a drop of ammonia, a very beauti- 

 ful oreenish fuliated or dendritic structure started from the 

 positive pole, and rushed towards the othex'. On withdrawing 

 the wires a little from each other, a new growth arose out of 

 the extremity of the previous formation, and generally on 

 coming within a certain distance of the negative pole it as- 

 sumed the metallic lustre. 



Galvanic action has been long known to coagulate albu- 

 men : on examining this action under the microscope this 

 thicker or white portion showed itself to be a vesicular struc- 

 ture which shrunk up in folds separated in several directions 

 by stronger integuments ; while the thin liquid which pre- 

 viously filled them, and gave them in a state of distension com- 

 plete transparency, spread over the glass dividing and drying 

 in compartments like those of a dragon-fly's wing. 



These statements will be ample to put any one in posses- 

 sion of the mode for making similar observations. Further 

 illustrations are unnecessary. The object of this notice is 

 merely to describe a simple arrangement for approaching 

 more nearly the phaenomena of chemical action. The micro- 

 scope will thus open to the chemist new and interminable 

 fields of faschiating inquiry, which cannot but have their use ; 

 for although in this mode of operating the several substances 

 must meet each other in unweighed and indefinite propor- 

 tions, yet the plan seems to hold out some advantages, at 

 least to facilitate the incipient processes of analysis, and to 

 serve as a guide to subsequent experiments of a more mea- 

 sured kind and on a larger scale. If the observation of re- 

 sults is recorded and classified, they must at last lead the 

 practised observer to more than conjectural conclusions as to 

 what he sees ; the visible effects under the action of certain 

 agents will become daily more accurately known, till at length 

 the microscopic examination of any substance will go very 

 far to establish its real character. 



N.B. Since this paper was read its author has applied a 

 micrometer to the microscope for measuring the angles of the 

 minutest crystals that appear on the field. A short notice of 

 this appeared in Jameson's Journal. 



