EDITORIAL OBSERVATIONS. 411 
perfect separation of different substances which could not be 
separated by any other means.” 
Dr. Miller, referring to this interesting method, as one of 
most extensive application, considers it necessary to put 
some ardent minds upon their guard, as many have hastily 
assumed, in a spirit of self-confidence, that we have already 
a key to everything on this subject. A possible way to a 
new truth has indeed been opened ; and here, doubtless, as in 
all other cases where we are permitted to obtain a further 
glimpse into the machinery of the universe, we shall but see 
fresh proofs of exhaustless wisdom on the part of the Great 
Author of nature; but instead of boasting of our triumphs, 
we shall, if we pursue our researches in a right spirit, be 
taught a lesson of reverent humility, as we are allowed to 
raise a fresh corner of the veil which separates that which is 
known to man from the infinitely greater portion which still 
lies beyond. Doubtless this branch of science is yet in its 
infancy, and therefore not yet perfectly systematised. 
An interesting lecture on this subject has lately been 
delivered at the Pharmaceutical Society of Great Britain by 
Professor Redwood, in which he says : 
“The term Dialysis has been applied by Mr. Graham to designate 
the separation of chemical atoms or molecules by liquid diffusion , that 
is, through the greater or less tendency which the molecules have to 
move from one part of a liquid menstruin to another, under particular 
circumstances. It is chemical analysis effected without the employment 
of chemical reagents, and it constitutes one of two very important ad¬ 
ditions which have recently been made to this department of practical 
chemistry. If it afford a less delicate means, as undoubtedly it does, 
of indicating the presence of minute quantities of chemical agents 
than that which is afforded by the method of Spectrum Analysis , it 
nevertheless admits of practical applications of which the other is not 
susceptible, for it enables us to separate bodies from each other, and 
doing this through the agency of physical forces inherent in the bodies 
themselves, it gives us results which are free from the influence inevi¬ 
tably exerted, in ordinary chemical analysis, by the reagents applied.” 
“ The term Diffusion has hitherto been principally applied to pheno¬ 
mena observed among gases and vapours. The diffusive property here 
is universal, and very important in its influences. No two gases can be 
brought into contact" with each other without the occurrence of diffu¬ 
sion.^ Thus, if we have two gases contained in separate vessels, such 
as two bottles, and if we establish a communication between them by 
means even of a small tube, the contents of one bottle will immediately 
flow into the other, and vice versa. This will even occur in opposition 
to gravity; for if the one gas be light, such as hydrogen, it will pass 
downwards into a heavy gas, such as carbonic acid, or sulphuretted 
