124 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



the objective of the microscope, and form a magnified image 

 upon a distant screen. At the proper moment we substitute 

 for the screen a sensitized photographic plate, and obtain a 

 photograph by the ordinary processes. A number of pict- 

 ures should be taken of the same object, in order to choose 

 among them that which presents the nature of the crystal- 

 line system under the best conditions. This precaution is 

 especially necessary in certain products, where the solution 

 gives results distinct from each other, according to the de- 

 gree of saturation. 13 .Z?, III., 171. 



EBULLITION PHENOMENA. 



Dr. Phipson states that water strongly acidified with hy- 

 drochloric acid, and containing a small quantity of ben- 

 zol, when placed over a spirit-lamp enters into a violent 

 ebullition every sixty seconds. After a while the boiling 

 ceases completely, and then recommences suddenly every 

 thirty seconds, for a considerable period. The flask still 

 being kept over the spirit-lamp, the periods between qui- 

 escence and violent ebullition dropped to twenty, ten, and 

 finally to eight seconds, at which intervals the phenomena 

 continued for a considerable time. 



When methyl alcohol was added to the above mixture of 

 water, hydrochloric acid, and benzol, and the flask placed 

 over a spirit-lamp, no ebullition at all occurred for a long 

 period of time, and then it took place suddenly and continued. 

 1 A, April 23, 1 11. 



ON THE RELATION BETWEEN SPECIFIC GRAVITY AND MAG- 

 NETISM OF IRON. 



From a number of experiments on the magnetism of iron 

 and steel, Holtz concludes that galvano-plastic iron receives 

 when made to glow by a galvanic current a greater specific 

 gravity. The molecules are brought closer together, the in- 

 tervals between them become smaller, and the permanent 

 magnetic moment is diminished by one half. On the other 

 hand, steel bars by being heated red-hot, and tempered, ac- 

 quire a smaller specific gravity, the molecules are farther 

 from each other than before, the intervals being greater, and 

 the magnetic moment is notably increased. Again, Wiede- 

 man has shown that permanent magnetism is diminished by 



