316 Progress of Invention. 



that the constituents of meteorites are iron and nickel, two 

 eminently magnetic metals. And it is not improbable that gravity- 

 is aided by magnetism, in attracting these bodies to the earth. 

 Only bodies, therefore, containing iron and nickel reach us, because 

 Gravity unassisted by magnetic attraction is unable to draw bodies 

 otherwise constituted out of their orbits. 



Steam applied to Railway Breaks. — The safety of a train not 

 unfrequently depends on the power of quickly bringing it to a state 

 of rest. This can be effected only by breaks. The more rapidly, 

 therefore, and powerfully these can be brought into action the more 

 they contribute to the safety of the train. Manual power, to be at 

 all effective, must be slow ; and hence, independently of its being 

 very limited in amount, an accident may occur before it has had suffi- 

 cient time to come properly into play. Steam therefore is now being 

 substituted in America for the muscular power of the breaksman, 

 and with most excellent effect. A steam cylinder of small bore, but 

 of considerable stroke is placed in the locomotive, under the driver's 

 foot board. The steam is turned on or off this cylinder, by means 

 of a handle which projects through the foot board. A chain which 

 acts on all the breaks of the train is attached to the extremity of 

 the piston rod. The pressure is never allowed to become so great 

 as to cause the Avheels to slide, that in the cylinder being 

 regulated by a safety valve attached to it. The power which may 

 be given to such a break is practically unlimited. That with which 

 the experiments were tried was capable of exerting a force of three 

 thousand five hundred pounds ; and of stopping within a space of 

 seven hundred feet, a train moving at the rate of fifty-six miles an 

 hour. 



New Preservative Compound. — Many substances have been em- 

 ployed for the preservation of animal matters, and with greater or 

 less success. Most of them are, however, liable to the objection of 

 difficult application or expense. A compound which is cheap and 

 easily applied, and is very effective, especially in the preservation of 

 anatomical specimens, has recently been discovered. It is made by 

 adding to about fourteen parts glycerine, two parts brown sugar, 

 and one part nitre ; the addition of the sugar and nitre being 

 discontinued as soon as a slight deposit begins to be formed. 

 Immersion in this fluid for a number of days, dependent on 

 the size of the object to be preserved, effectually preserves 

 organic substances from putrefaction, without, at the same time, 

 altering their appearance. When first lifted out they will indeed, 

 be in the highest degree rigid, but on being placed for a while in a 

 warm dry place they will become as pliant as ever. 



New Explosive Compound. — Experiments made on the effects 

 produced by nitrate or chlorate of potash on glue have led to the 

 discovery of a new and extremely cheap explosive compound, which 

 may be employed with special advantage in conjunction with ordi- 

 nary gunpowder. This compound may be obtained by either of two 

 methods. According to one of them, two parts glue arc washed 

 with cold water ; then heated '^moderately with a small quantity of 

 nitric acid, evaporated, again mixed with water, and freed from 



