April, 1918 C. U. C. P. ALUMNI JOURNAL 55 



writer is rapid and appears to be certain. It has been used in the examination 

 of all samples suspected of containing glass received at this laboratory in the 

 past three months, as well as numerous test samples made up by myself and 

 containing glass fragments of different sizes and from various sources. Fine 

 sand particles and glass fragments when viewed through the microscope may 

 appear very similar, although sand grains frequently show evidences of erosion 

 whereby the edges are worn way. Pieces of glass are usually clear and 

 sharp edged. However, I have found that many sand particles are clear and 

 possess sharp edges and angles. The behavior of sand particles and glass frag- 

 ments subjected to microscopical examination using an instrument fitted with a 

 polarizing apparatus appears to be a ready means of distinguishing one from the 

 other. Sand grains in the dark field or crossed prisms stand out in white or 

 often show a beautiful play of colors, blue usually predominating. Glass par- 

 ticles with the same treatment remain dark in the field and no coloration was 

 found in any of the test samples examined. Use of a selenite plate (red ^/^ or i) 

 with crossed prisms gives especially fine color effects in the case of sand grains; 

 whereas glass fragments remain of red color in the red field. Use of comparatively 

 low magnifications is advisable and in the routine examinations i6mm. or 8nini. 

 objectives with 7.5X or lox oculars were used. 



The following statistics are given to show how little ground there is for 

 apprehension in this "glass scare". The figures are authoritative, rest upon actual 

 fact, and not mere rumor or presumption and are taken from the laboratory 

 records of analyses performed by the writer since the beginning of the agitation. 

 Among the samples received for analysis are many items from the Federal 

 Food Board of New York City (U. S. Food Administration) and the Police 

 Department, although the greater number were collected by inspectors of the 

 Department of Health either upon complaint or assignment. 



Materials submitted ^Zlples" ' «^"^ ^Tnl subt!n?tted ^Jff.^X^ 



examined P^^^'^"* "^^^^^^ with sample •" sample 



Sug^ars and syrups 24. 



10 14 



Tomatoes 8 5 3 



Meals 12 2 10 1 



Flours 39.... 13 26 



Breads 92 26 64 15 2 



Jam.... 9 6 3 



Cheese 2 2 



Candy 60 41 15 



Crackers, cake, pie 16 9 6 



Icecream 4 2 2 1 



Macaroni 3 2 1 1 



Oysters 1 1 



Peanut butter , 3 3 



Fish ■■ 5... -. 3- 2. .0^ - 



Totals 278 123 148 25 7 



4 4 



3 1 



