164 



THE AMEKICAN MONTHLY 



[September, 



like the eggs of insects (fig. i). Place 

 a second portion of the same butter 

 on a glass slide 3X1 inches ; com- 

 bine 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 

 transmitted light, when crystals like 

 fig. 2 will be 'seen. Second, by 



«goyo°ogo 



O O O qO 



ili^ 



Fig. 26, — Butter and Fat. 



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 analyz- 

 ing prism above. Under these con- 

 ditions a dark ground is produced, 

 and the butter crystals, which are 

 globular in fonn, are seen in bold re- 

 lief. The butter globular crystals will 

 now exhibit a well-defined black cross 

 representing that known as vSt. An- 



drew's (fig. 3). Figure 4 represents 

 a crystal of butter showing divisions 

 produced in prismatic colors when 

 the selenite plate is used with polar- 

 ized light. If old butter or a poor 

 oily butter is used in this experiment, 

 the secondary crystals of butter ai"e 

 generally showai. These crystals are 

 of rosette form, much smaller than 

 that of the globular, and exhibit no 

 cross (fig. 6) . 



The globular crystals of butter, 

 when kept for a inonth or more, seem 

 to bud like a vegetable spore, and 

 frequently every round crystal will 

 show projecting from each a smaller 

 crystal (fig. 5). The globular forms 

 generally vary from fifteen ten-thou- 

 sandths of an inch to the one-hun- 

 dredth of an inch in diameter. These 

 forms are never seen in pure beef or 

 lard fats. Care should be observed 

 not to press the crystals flat, espec- 

 ially 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, shows on its crystals indenta- 

 tions, a condition represented in no 

 other butter yet observed. The but- 

 ter crystals seen in the butter made at 

 Mr. Frank Ward's dairy of Washing- 

 ton, from milk of Alderney cows, also 

 dift'er in some particulars from all 

 others examined, being darker in 

 color, spines longer, and of larger 

 size. Specimens intended for per- 

 manent use should be mounted with 

 a varnish ring, to prevent the cover 

 from pressing on the crystals, and to 

 prevent the movement of the cover 

 used to protect them. 



Explanation of Figures. 



1. Represents crystals of boiled butter as seen by a 



pocket lens. 



2. A single crystal of butter, highly magnified, viewed 



by transmitted light only. 



3. A crystal of butter viewed by polarized light only. 



It exhibits the cross of St. Andrew. 



4. A crystal of butter as seen under polarized light 



and selenite plate. In this case beautiful colors 

 are displayed, while the cross is but faintly seen. 



5. Represents what seems to be a budding butter crys- 



tal. 



6. Represents the rosette crystals of butter. 



7. The crystalline form of lard. 



8. The crystalline form of beef. 



