xliv GENERAL SUMMARY OF SCIENTIFIC AND 



continuously, and if the temperature of the ice and of its sur- 

 roundings be near the melting point. In one experiment a 

 hollow iron cylinder 11.5 millimeters in diameter sunk into 

 the ice 3 millimeters in two hours, it being surrounded with 

 snow, the temperature varying from 1 to -f 0.5. When 

 the temperature rose above the melting point, it sank 3 cen- 

 timeters in one hour ! scarcely a trace of water resulting. A 

 steel rod a square centimeter in section, when pressed with 

 one third of an atmosphere, sank into the ice 14 millimeters 

 in three hours, the temperature being 2.5. The flexibility 

 of ice was shown by placing a parallelopiped 52 centimeters 

 long, 2.5 centimeters broad, and 1.3 centimeters thick upon 

 wooden supports placed near its ends. From February 8 to 

 15, the temperature varying from 12 to 3.5, the mid- 

 dle portion sank only 11.5 millimeters. But the succeeding 

 twenty-four hours the temperature was higher, and the mid- 

 dle of the bar sank 9 millimeters. From 8 A.M. to 2 P.M. 

 the increase was 3 millimeters, when the bar broke, the tem- 

 perature being +3. The whole bending was 23.5 millime- 

 ters. Similar experiments were made upon the ductility of 

 ice ; it elongated by traction. From these results it is easily 

 seen why a glacier's motion increases with the temperature. 



Professor Nipher has made an elaborate investigation upon 

 the mechanical work done by a muscle before exhaustion, 

 the data given being more accurately determined than those 

 published by him three or four years ago, and adopted as a 

 basis for calculation by Professor Haughton, of Dublin. 



De la Bastie has communicated to the Societe d'Encourao-e- 

 ment an account of his new process of tempering or harden- 

 ing glass. The manufactured articles are heated to near the 

 temperature of softening, and then cooled suddenly in a suit- 

 able bath of oil. The glass thus treated becomes extraordi- 

 narily resistant, in some cases amounting to fifty times that 

 of ordinary glass. It becomes also very hard, so that diffi- 

 culty is experienced in cutting it with a diamond. Though 

 so resistant, it is very brittle. A piece when broken flies into 

 a thousand fragments, exactly like the well-known Prince 

 Rupert's drop. Vessels were shown of the new glass in 

 which water could be boiled over a naked fire without fear 

 of breaking them. Upon plates of it a weight of one hun- 

 dred grammes was allowed to fall from a height of three 



