EEPOllT OF THE SIICIIOSCOPIST. 95 



Frequent occasion for exi)erinieDt has since beeu afforded, in tests of 

 butter samples of uncertain or suspicious origin, and I have made the 

 di.svoverv that when it is boiled and cooled slowly for a period of 

 twenty-four hours, at a temperature of from 50^ to 70° F., it not only 

 becomes crystallized, but, with i)roper mounting and the use of i>olarized 

 liglit, it exhibits on each crystal a welldetinod iigure, resembling wlmt 

 is known as the cross of St. Andrew. In course of time, tlie period 

 ranging from a few days to a lew weeks, according to the quality of the 

 butler used and the tenqieraturc to whicli it i« exposed, the cryst;i!s. 

 which at iirst are globular, degenerate, giving way to numerous ri>si'Hc- 

 like forms ])ecuiiar to butter. 



1 have also demonstrated that tlic crystals of butter and lard re- 

 spectively differ essentially from each otiu-r, and may be ilistinguishiMl 

 at once, one from the other, wlien i)roperly prepared. The crystals of 

 newly-made butter, when boiled, are globular and present a (h)tied aj)- 

 pearance, due to the projection of numerous short spines. TImse. of 

 beef have long biserrated spines proceeding from a. common center, 

 Avhile lard gives a strictly stellar or star-like form, proceeding from a 

 dense, opaque centci, which appears to bo granulated. 



These new facts led me to experiment with other fats, vegetable and 

 animal, with a view to determining wiiether the fats of other animals 

 and of vegetables may not have, otlier crystalline forms peculiar to them- 

 selves, and of such detinite structure as might lead to their detection 

 when fraudulently combined with other iats in medicinal compounds, 

 &c. I have made numerous experiments to that end, ami have found 

 that the normal crystals of several fats, which have not heretofore beesi 

 examined with sutiicient accuracj', maybe distinguished from all others 

 thus far examijied. For exiiui|)le, cacao butter, when its consistency is 

 A^ery much reduced with sweet oil, gives a most beautiful and perfect 

 discoid crystal. Si)ermaceti, white beeswax and paraOine, treated in 

 the same way give other lorms, but as yet I am unable to obtain the 

 highest crystalline forms of these last-mentioned fats. 



The utility of these investigations in animal and vegetable fats niay 

 be in/erred from the fact that in each of the prosecutions lately brought 

 against fraudulent butter dealers and venders, in the city of Washing- 

 ton, the accused, in every instance, acknowledged that my evidence 

 against them was correct, and that they had sold tallow compounds as 

 butter. 



As a result of this detection of fraudulent compoutuls, about sixty 

 hawkers, men and women, who, under the guise of fainiers, liave been 

 otfering for sale, from door to door, compounds of tallow, lunl, and cot- 

 ton-seed oil, mixed with inferior butter, as genuine creamery butter, 

 have abandoned their calling. 



EXAIVnNATION OF UUTTEIl AND ITS SUBSTITUTES. 



In making examinations of butter and its substitutes, a si)e(iinen of 

 t;he suspected article is placed betv.'eeu two small pieces of glass, using 

 •or one the ordinary microscoi>ic slide 3 by 1 inch, an<l f<u- the other a 

 thick microscopic disk; then compress the specimen sulliciently to give 

 a thin translucent cloud. If white oi>aque particles are observed be- 

 tween the glasses, there is reason to believe that the substance is a 

 fatty compound. If the experimenter w ill first practice with lard in an 

 atnjosphere of moderate temperature, he will observe the white specks 

 of fat alluded to. Should the cloud be very even throughout, it is 

 probably either pure butter or newly-made butteriue. 



