224 Tue Microscope. 
by him—that the microscopic methods of Dr. Taylor, for the dif- 
ferentiation of butter and other fats had no practical value in the 
examination of adulterations, the only direction in which such a 
method is of any necessity. 
Prof. Weber illustrated his paper by quite a number of ‘ blue 
prints” made from negatives by Dr. A. J. Detmers. 
Dr. Taylor in replying, showed on the blackboard, the appear- 
ance of the different crystals, etc., and commenced by alluding to 
the first three experiments made by Prof. Weber in relation to the 
crystals of butter, lard and oleo fat. Here Dr. Taylor called at- 
tention to the fact that Prof. Weber acknowledged that thus far Dr. 
Taylor’s statements in relation to the forms of the three respective 
fats named were verified. The next following three experiments of 
Prof. Weber were reviewed by Dr. Taylor. They related to three 
different compounds of butter and lard. The first composition 
consists of ninety parts butter and ten parts lard ; second compo- 
sition seventy-five parts butter, twenty-five parts lard ; third com- 
position fifty parts butter, fifty of lard. Each of these composi- 
tions was boiled, cooled and examined by Prof. Weber. He says 
all exhibited the butter crystal. To these three experiments Dr. 
Taylor objected because they did not represent his method of test- 
ing for oleomargarine. Dr. Taylor in his annual report to the Com- 
missioner of Agriculture sets forth that it is absolutely necessary to 
examine all butter substitutes as purchased. By this means the 
crystals of lard, if present, are at once detected by means of the 
microscope. The object being to distinguish foreign fats, such as 
lard and beef, which are never found in pure butter, Dr. Taylor 
explained that it was a great error on the part of Prof. Weber to 
boil a suspected butter on receiving it, because were butter pres- 
ent in quantity in combination with lard and beef fat, the foreign 
crystals would be absorbed by the large butter crystals formed by 
the process of boiling. It should be observed that lard and beef 
fats have passed through the process of boiling, while the butter 
combined with it has simply been melted at a low temperature. 
In normal oleomargarine their crystals are already formed while 
the butter shows none unless boiled. To a superficial observer 
boiled oleomargarine, if it contain much butter, would appear 
true butter instead of oleomargarine. Whereas, by first making a 
