ON THE ANIMAL FLUIDS.' 43 



and not on account of an hypothetical new channel, a sort 

 of northwest passage from the stomach to the unnary blad- 

 der. In the case of waters the proportion is so minute of 

 various impregnating substances, that, unless very large 

 bulks be used, they must escape detection. The great mas- 

 ters have accordingly u?ed such large quantities. Margraf, 

 (Opuscules chymiques, v. II, p. 8) did not evaporate 

 100 drops of snow or rain water in a watch giass capsule like 

 some modern microscopic chemists, but he operated upon. 

 100 quart measures of snow water, in which he was able to • 

 find only 60 grains of carbonate of lime, a few grains of 

 muriate of soda, arid traces of nitrous acid. 



I had the advantage of making my juvenile efforts to per* 

 form several chemical exercises under that great master, 

 professor Black. Among other precepts, treasured in the 

 tablet of ray memory for more than 30 years, was that of 

 employing large bulks of mineral waters ; and of all other 

 things, in which there was a probability of minute proper-* 

 tions being present. The reasons of Dr. Black for not 

 practising according to this rule in the insiance of the ana- 

 lysis mentioned I cannot pretend »o assign ; but it seems 

 probable, that he was in possession of only a small quantity 

 of the material. As to the magnitude of the musses of mat* 

 ter required, it is impossible to specify them ; but it is ob- 

 vious, that analysis must fail to develope substances on ac«» 

 count of the minute proportion to other things with which 

 mixed not being susceptible of being made evident to the. 

 senses; and in consequence, by a due larger proportion 

 they may be rendered sensible. Hence perhaps, it is that 

 we are ignorant of many of the properties of iight, calorific, 

 electricity, of infectious, and contagious substances, &c. It 

 19 argued against me, that " the chemical properties, which 

 belong to a particle of matter, belong to the whole moun- 

 tain of the same substance." True — but I know nothing 

 of properties of substances but by means of the external or- 

 gans of sensej (this is indeed an axiom) and unless the par- 

 ticle be of a dne magnitude, my organs of sense cannot in- 

 form me of its pioperties. 



My honourable adversary talks of the advantage of a small Advantages «f 

 l?cale of operation in the points of economy and convenience, o/^eratiow 



Granted-*. 



