

The Microscope. 213 



although they appear very interesting objects with a power as 

 low as 80. 



When it is desired to examine the crystals of butter, boil 

 about an ounce of pure, newly-made butter in a test tube or iron 

 spoon for a period of several seconds ; allow it to cool as directed 

 in the case of beef and lard ; place a few grains of it on a slip of 

 glass; pour over it a few drops of alcohol, (or better, with alco- 

 hol nine parts, carbolic acid one part;) separate the crystals 

 with a pin, and view them with a pocket lens ; they will appear 

 like the eggs of insects, Fig. 1. Place a second portion of the 

 same butter on a glass slide 3x1 inches ; combine it with a drop 

 of sweet oil by means of a pin, reducing the butter to granules ; 

 cover with a thick disc of glass, and view first with plain trans- 

 mitted light, when crystals like Fig. 2 will be seen. Second, by 

 polarized light. In this case place the polarizer low down and 

 turn this prism round until its face angle crosses the face angle 

 of the analyzing prism above. Under these conditions a dark 

 ground is produced, and the butter crystals, which are globular 

 in form, are seen in bold relief. The butter globular crystals 

 will now exhibit a well defined black cross representing that 

 known as St. Andrew's. See Fig. 3. Figure 4 represents a crys- 

 tal of butter showing divisions produced in prismatic colors 

 when the selenite plate is used with j)olarized light. If old but- 

 ter or a poor oily butter is used in this experiment, the secondary 

 crystals of butter are generally shown. These crystals are of 

 rosette form, much smaller than that of the globular, and exhibit 

 no cross. See Fig. 6. 



The globular crystals of butter, when kept for a month or 

 more, seem to bud like a vegetable spore, and frequently every 

 round crystal will show projecting from each a smaller crystal. 

 See Fig. 5. The globular forms generally vary from fifteen ten- 

 thousandths of an inch to the one-hundredth of an inch in di- 

 ameter. These forms are never seen in pure beef or lard fats. 

 Care should be observed not to press the crystals fiat, especially 

 the globular crystals, as the cross is not seen when severely 

 pressed. 



Butter crystals vary slightly from each other in size and in 

 some other slight particulars, such as color. A butter received 

 from Tennessee, made from milk of Holstein and native breed, 



