610 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



cannot be placed further back than the time when the temperature of the Po- 

 lar regions was 122 deg. fahrenheit, at which degree albunrien coagulates. 

 He directs attention to the subsequent p riod, but so much later that the 

 lapse of time is beyond our conception, when Great Britain had cooled to 

 that temperature, and from calculations and data given, he proves that the 

 time which felapsed before the mean temperature of the island had fallen to 

 7t deg., in consequence of the coolness of the earth, to be 1,018,000,000 of 

 years. This is the London clay tertiary epoch, during which mollusks in- 

 habited the seas of Great Britain. 



The Chair directed attention to the interesting fact just stated, that 

 albumen, an essential element in animal organization, coagulates at 122 

 degrees F., or 50 degrees Centigrade, which is just midway between the 

 freezing and boiling point of water, although in solution, as iu the blood 

 for instance, the coagulating point is much higher. 



Mr. Maynard said from experiments he had made with milk, he concluded 

 that it coagulated at a higher temperature than now stated. 



Dr. Parmelee reminded the last speaker that albumen is not found in 

 milk. The casein of milk closely resembles both fibrin and albumen, and 

 is readily converted into them by the digestive process. Casein is not, 

 like albumen, coagulated when heated. 



Wrought Iron Girders. 



William Fairbain, F. K. S., read before the Royal Society, February 4, a 

 paper entitled "Experiments to determine the effects of impact vibratory 

 action and long continued change of load on wrought iron girders," in 

 which he describes his experiments to determine the strength and form of 

 iron tubular bridges, also to show the extent of strain to which an iron 

 girder may be subjected. His apparatus was designed to imitate as nearly 

 as possible the strain to which bridges are subjected by the passage of 

 heavy trains, by lowering the load quickly upon the beam and by producing 

 a considerable amount of vibration. The test girder was a wrought iron 

 plate beam twenty feet long. Upon it a weight was allowed to fall at 

 intervals of about eighty per minute, day and night, by means of a mill 

 driven by water power. The conclusion drawn from these experiments is 

 that wrought iron girders arc not safe when subjected to violent disturb- 

 ances equivalent to one-third of the weight that would break them, but 

 when they are equivalent to one-fourth of the weight the tenacity is unim- 

 paired. 



Iu the brief discussion on this item Mr. Stetson said he esteemed the 

 matter mainly for its attempt to give the exact degree of strains which, 

 begin to be destructive. The fact that great strains approaching near the 

 breaking point would, if continued under such conditions, impair the char- 

 acter of the material, was generally acknowledged. 



Mr. Garvej^ alluded to the fact that constant vibratory motion tends to 

 disintegrate wrought iron, by producing a crystalline arrangement of its 

 atoms. 



Mr. Fisher said it was the opinion of the late I. K. Brunei, of England, 

 that the peculiar molecular arrangement described by the last speaker was 



