194 ANNUAL OF SCIENTIFIC DISCOVERY. 



some pieces of large calibre, had a machine constructed for measuring the 

 force exerted by the wind of balls par-sing at various distances. The results 

 obtained were constantly the same. At the distance of three inches, a pass- 

 ing ball produced not the slightest effect. The conclusions deduced by Mr. 

 Pelikan are: 1. A projectile passing very close to any object exercises only 

 an insignificant influence upon it. 2. That what is called the wind of the 

 ball, even with a full charge of powder, has so trifling a force as to be inca- 

 pable of determining any lesion. 



LUNAR TIDE UPON LAKE MICHIGAN. 



At a meeting of the Chicago Historical Society, November 30th, 1858, Col. 

 Graham, U. S. A., stated, as the result of a long and carefully conducted 

 series of observations, his discovery of a lunar tidal wave upon Lake Michi- 

 gan. From the comparatively small area of the body of water acted upon 

 by the lunar influence, the coordinate of altitude could not be but small. 

 This circumstance, added to that of the almost constant disturbance of the 

 lake surface by winds, renders this coordinate of altitude measurable only 

 in calm weather, and when the moon is in conjunction with or in opposition 

 to the sun. At such times its average is about two-teiiths of a foot, or say 

 two and one-half inches. 



UNITS OF WORK. 



The following are the results obtained in units of work or foot-pounds for 

 one unit of heat, by different authors : 



Centigrade Fahrenheit 



thermometer. thermometer. 



Foot-pounds. Foot-pounds. 



By Holtzman's formula, ..... 1227 682 



By Joule's experiments, 1386 770 



By Rankine's formula, 1252 695 



By Thompson's formula, 1390 772 



For the best Cornish engine, by M. De Tambour, 148 82 



For a perfect low-pressure condensing engine, . 90'8 50-4 



For an actual Boulton and Watt's engine, . 46 25 5 



ON THE STRENGTH AND TENACITY OF GLASS. 



A series of interesting experiments have been recently made in England 

 on the strength and tenacity of glass. By tearing rods and sheets of glass 

 asunder, the following mean results of tenacity per square inch, expressed in 

 pounds, were obtained: Flint glass, 2.413; green glass, 2.826; crown, 2.9-16. 

 The experiments on the resistance offered by glass to a crashing force, were 

 made upon small cubes and cylinders, crushed between parallel steel sur- 

 faces, by means of a lever the force employed being sufficient to reduce the 

 glass to a fine powder. The results, expressed in pounds, were as follows : 

 Flint glass, 13.190; green glass, 20.206; crown, 21,867. 



BLASTING WITH GUN-COTTON. 



It is generally said that gun-cotton produces three times the effect of gun- 

 powder; but military engineers aver that the effect which the explosion of a 

 certain quantity of gun-cotton will produce, can never be exactly foretold. 

 If the cotton is very strongly compressed when the electric spark is applied 



