624 Transactions of the American Institute. 



used in a Bunsen burner to heat a clean platina dish containing 

 water. After evaporating about a pint of water, the outside of the 

 vessel will be found to be partly coated with an oily fluid, which can 

 be distinctly shown, by ordinary qualitative tests, to be sulphuric 

 acid. The same author states that the' white incrustation which 

 sometimes makes its appearance on the inside of the lamp chimneys 

 consists of sulphate of ammonia. 



III. A Great Electro-magnet. 



The Stevens Institute of Technology has an electro-magnet, made 

 in Ansonia, Conn., which weighs about 1,600 pounds, and has a lift- 

 ing force estimated at between thirty and fifty tons. About 400 

 pounds of copper wire, one-fifth of an inch thick, is wound on eight 

 spools, each nine and one-half inches high by eleven and one-half 

 inches external diameter. The cores are hollow, and six inches in 

 diameter by three feet three inches in length. This magnet is about 

 five times as powerful as that used by Faraday in his famous researches. 



TV. Test for the Presence of Ozone. 

 M. Lamy has recently published in a Paris journal the results of 

 his experiments in obtaining reagents for ozone. He says that paper 

 moistened with the oxide of thallium, when freshly prepared, is far 

 more sensitive to ozone than that prepared with the iodide of potas- 

 sium and starch. "When a rapid and trustworthy test of the presence 

 of ozone in the atmosphere is desired, the oxide of thallium is recom- 

 mended ; but it should be understood that the sensitiveness of this 

 reagent depends on the strength of the solution and the extent to 

 which the oxide has absorbed carbonic acid. 



Y. Colors Changed by Heat. 

 5. Prof. E. Gr. Houston and Mr. Elihu Thompson, of the Central 

 High School of Philadelphia, have recently made a series of experi- 

 ments to ascertain the law by which the color of various salts and 

 oxides are changed by the action of obscure heat rays. The sub- 

 stances under examination were placed, in the state of diy powder, on 

 strips of sheet-copper, which were heated by means of an ordinary 

 Bunsen burner. Colored bodies which did not return to their original 

 tint on being cooled were excluded from the experiment. It was 

 found that in all cases in which the color of the body is changed by the 

 application of heat, and the original color regained on cooling, the 

 nature of the body being in no wise altered, the character of the 



