Polytechnic Association Proceedings. 725 



The result of this operation is a gaseous mixture of oxj-gen and 

 fluorine; from this the oxygen is abstracted by passing the mixture 

 over heated oxide of barium (baramaC). The binoxide of barium 

 (baramei) is formed while the fluorine is left in the form of a gas. 

 M. Prat states it is colorless, and has an odor resembling chlorine. 

 It decolorizes indigo; reddens litmus; fumes on coming in contact 

 with air; gives dense fumes with ammonia (gilan)', decomposes 

 water, as well as hydrochloric acid {galad)] unites with hydrogen 

 in difi'use light, forming hydro-fluoric acid (alaf); and last, it 

 combines with all metals, excepting, perhaps, platinum and gold. 

 M. Prat's experiments are to be repeated before a committee from 

 the French Academy of Sciences. He seems to have selected a 

 most direct path to success by first obtaining a mixture of two 

 gases, which it is well known do not combine chemically. 



THE INTERNAL HEAT OF THE EARTH. 



Dr. Julius Schavarez read a paper on this subject before the 

 British Association, in which he concludes that the difierent corol- 

 laries of the central fire doctrine were not adequate to explain the 

 difierent groups of natural phenomena for the sake of which these 

 corollai'ies were deemed essential fifty years ago. He adds some 

 suggestions as to how experiments should be made, in order to 

 ascertain the temperature of the earth at difierent depths, simulta- 

 neously in difierent quarters of the globe. Sir Charles Lyell said 

 he was glad to know that the subject of underground temperature 

 was to be taken up at the expense of the British Association. He 

 had long been convinced that so far as the evidence now goes, there 

 is an increase of temperature very generally as we descend from 

 the surface of the earth as far into the interior as we can enter, but 

 it is a mistake to suppose that the best observations indicate a uni- 

 form increase. That he believed, would be one of the results of 

 the inquiry, but it would also be a great pomt to ascertain what 

 was the amount of difierence of temperature at difierent places. 



• A NEW ELECTRIC LIGHT. 



An exhibition of the working of a new method for producing 

 light by means of electricity, the invention of Prof. Nollet of Paris, 

 was made at the Battery in New York, on the 15th inst. The 

 illuminating apparatus having been placed on the roof of the Barge 

 office, threw a very clear and penetrating light to a great distance. 

 So strong was the light, that the captain of one of the revenue 



