608 Uxperiments with Cast Iron^ etc. [December. 



Experiments with Cast Iron. — The interesting fact has been 

 developed by experiments of the Ordinance Department, that iron, 

 by repeated fusion up to a certain number of times, is thereby greatly 

 improved in strength. Guns cast solidly, and those cast hollow, 

 through which latter water was made to circulate after casting, showed 

 an astonishing difference in their relative strength, difference being 

 in favor of the hollow cast gun, which is attributed to the method of 

 cooling — the solid gun, contracting from the outside, exerting a 

 strain upon the arrangement of the particles of the metal in the 

 same manner or direction as the strain of the discharger. The ex- 

 periment also showed that old castings area great deal stronger than 

 new. Eight-inch guns, proved thirty days after being cast solid, 

 stood but 72 charges ; thirty-four days, 84 charges ; one hundred 

 days, 731 charges ; and six years, 2,582 charges. This phenomenon 

 is accounted for by supposing that the particles strained in the cool- 

 ing, re-adjust themselves in the course of time to their position, and 

 become free or nearly so. 



How MUCH SHOULD A Cow Eat? — Cows, to give milk, require 

 more food than most farmers imagine. J. W. Johnson, writing from 

 Munich to the Covntry GentJe^nan^ gives an interesting report of 

 some experiments which have been made in Bavaria, from which the 

 following is an extract : — " Our trials have confirmed the view that 

 cows, to give the greatest possible quantity of milk, must daily re- 

 ceive and consumxC one thirtieth of their live weight in hay, or an 

 equivalent therefor. If more food be given, it goes to the formation 

 of flesh and fat, without occasioning a corresponding increase in the 

 yield of milk ; but if, on the contrary, less food be furnished, the 

 amount and value of the milk will be greatly diminished." 



Water running up Hill. — Dr, Smith, in a lecture on geology, 

 at New York, mentioned a curious circumstance connected with the 

 Mississippi River. It runs from north to south, and its mouth is ac- 

 tually four miles higher than its source, a result due to the centrifu- 

 gal motion of the earth. Thirteen miles is the diiFerence between 

 the equatorial and polar radius ; and the river, in two thousand 

 miles, has to rise one-third of this distance, it being the hight of 

 the equator above the pole. If this centrifugal force were not con 

 tinned, the river must flow back, and the ocean would overflow the 

 land. 



