190 ANNUAL OF SCIENTIFIC DISCOVERY. 



5 per cent, of litharge was also affected, but far less perceptibly ; 

 crystal glass, made with carbonate of potassa (the other varieties 

 referred to contain carbonate of soda), litharge, and silica, was 

 not at all affected ; English plate glass, made by the British Plate 

 Glass Company, and exhibiting a distinctly azure-blue tinge, 

 remained, also, unaffected. The author attributes this coloration, 

 wiiich begins witli yellow and gradually turns to violet, passing 

 through red pelurc d'oignon, to the oxidizing effect of the sun\s 

 rays upon the protoxides of iron and manganese contained in 

 glass. — Comptea Rendus, Nov. 22, 1869. 



Luminous Effects of Light. — In the ** Coraptes Rendus," of 

 Nov. 15, there is a paper entitled, "Researches on the Luminous 

 Effects due to the Action of Light upon different Bodies." Tliis 

 is the fifth instalment of a lengthy memoir by M. Becquerel. 

 The author's experiments lead to the following conclusions : 

 The most refrangible rays, and principally those beyond the 

 violet, are the most active ; the different parts of tlie solar spec- 

 trum differ in their activity ; the least refrangible rays from the 

 blue, and past the ultra-red, act especially as extinguishers of 

 phosphorescences. 



Phosphorescence of the Sea. — The phenomenon is due to elec- 

 tricity, and the infusoria only acts as sharp points do in well- 

 known electrical experiments. — M. Duchemiiiy Comptes RcnduSy 

 Nov. 2, 1869. 



Constitution and Motion of Glaciers. — In the "Comptes Ren- 

 dus," of jSTov. 2, 1869, MM. Grad and Dupre have a paper on 

 this subject. 



Tlie chief results of the labors of these authors are the follow- 

 ing : Tiie crystals of ice of the glaciers are arranged in a regular 

 manner, and the constituent molecules of that ice are placed as 

 in frozen water. The velocity of motion of a glacier increases 

 from the bottom to the top, while the maximum of motion coin- 

 cides with the greatest slope. 



Reflection of Heat. — Professor Gustav Magnus, at the meeting 

 of the British Associatiop, read a paper, in which he made known 

 a curious discover}^ of his own, that lluor spar has the property of 

 reflecling, very largely, the dark, invisible rays emitted by hot 

 n^ck salt. Dr. Balfour Stewart then called attention to the fact 

 that there is much evidence tending to prove that the heat rays 

 from rock salt are of very great wave length, belonging almost 

 to one of the extremities of tlie spectrum. 



Mechanical Equivalent of Ueat. — Mr. P. H. Van der Weyde, 

 of New York, read a paper, at the meeting of the American 

 Association, Aug., 1869, on "The Determination of the Mechan- 

 ical Equivalent of Heat by Means of the Modern Ice and Cooling 

 ^Lichines." In converting heat into motion there is a great loss, 

 the result being but one-seventh or one-fourteenth part what 

 would be expected. But in converting motion into heat we get 

 very nearly a full equivalent. In the production of artificial cold 

 by al)straciing heat we get the same result. The expenditure of 

 one horse -power reduces the temperature of water one degree 

 Fahrenheit in one minute. In the English process of cooling, 



