NATURAL PHILOSOPHY. 87 



at the last meeting of the British Association, by means of a new in- 

 strument invented by M. Bourdon, of Paris, and called the " Injector 

 of Solids." 



Giffard's injector consists of three tubes united at one point : one of 

 these brings the supply of water for the boiler from any convenient 

 source ; the second is for the purpose of conveying the water into the 

 boiler, and opens below the level of the liquid in that vessel ; the third 

 brings a jet of steam from the upper part of the boiler. This jet of 

 steam has the power of injecting a constant supply of water into the 

 boiler, and so obviating altogether the necessity for a feed pump, and, 

 apparently impossible as it may appear, not only has the steam power 

 to inject water into its own boiler, but is capable of feeding another 

 boiler in which the steam has a much higher pressure than itself. 



M. Bourdon's Injector of Solids, which is capable of rendering this 

 action visible by means of solid bodies, consists of two air vessels, with 

 a communicating tube capable of being opened or closed at the will of 

 the experimenter. One of these vessels is made of glass, and furnished 

 with an aperture closed by a valve opening inwards. The other has a 

 small air-gun proceeding from it, the barrel of which is directed against 

 the opening in the first vessel. On condensing air into the two re- 

 ceivers, it is found that, even when four atmospheres are condensed into 

 the glass vessel, and only two in that connected with the air-gun, the 

 bullet driven by the latter has power to open the valve closed by the 

 pressure of four atmospheres and enter the glass receiver. 



ESTIMATION OF DISTANCES AND SPEED. 



Many people hear of distances in thousands of yards a usual meas- 

 ure of artillery distances, and have very little power of reducing 

 them at once to miles. Now, four miles are ten yards for each mile 

 above 7,000 yards, whence the following rule : the number of thou- 

 sands multiplied by four and divided by seven gives miles and sevenths 

 for quotient and remainder, with only at the rate of ten yards to a mile 

 in excess. Thus 12,000 yards is 4-f- of a mile, or G-| miles; not 70 

 yards too great. Again, people measure speed by miles per hour, the 

 mile and the hour being too long for the judgment of distance and 

 time. Take half as much again as the number of miles per hour, and 

 you have the number of feet per second, too great by one in thirty. 

 Thus 16 miles an hour is 16-}-8, or 24 feet per second, too much by |-A 

 of a foot. London Athenceum. 



POWER OF WAVES. 



The Paris Cosmos, in describing the effects of a stormy period in. 

 January, 1863, on the coast of France, gives instances where "blocks 

 of stone weighing thirteen tons were hurled to a distance of more than 

 thirty feet, and blocks of three tons to more than one hundred yards. 

 The outer harbor of Fecamp was destroyed, and the mass of earth torn 

 from the north side of Cape la Heve was estimated at more than 

 300,000 square yards." 



MOTIONS OF CAMPHOR UPON WATER. 



When small pieces of camphor are dropped on the surface of a glass 

 of water, several curious phenomena may be observed. They im- 



