PHENOMENA OBSERVED IN PROVING THE STRENGTH OF IRON BARS. 



131 



simply from the metal being oxidized to 

 a minimum, and diffused by the agency 

 of a mild acid through a great body of 

 water, in which state it is rapidly taken 

 up by the lacteals, and speedily imparts 

 a ruddy hue to the wan countenance. — 

 I find that these qualities may be imitated 

 exactly by dissolving three grains of 

 sulphate of iron, and sixty grains of 

 bicarbonate of potash in a quart of cool 

 water with agitation in a close vessel. 



Ure. — ib. 



ACTION OF SULPHUR ON IRON. 



Colonel A. Evans has remarked that 

 although sulphur has so strong an action 

 on heated wrought iron as immediately 

 to form holes in it, yet it does not at all 

 affect gray cast iron. A plate of wrought 

 iron, .63 of an inch in thickness, heated 

 to whiteness, and held against a roil of 

 sulphur, -f^ of an inch in diam.eter, was 

 in fourteen seconds pierced through with 

 a perfectly cylindrical hole. Another 

 bar, about 2 inches in thickness, was 

 pierced by the same means in fifteen 

 seconds. 



Good steel was pierced even more 

 rapidly than the iron, but a piece of gray 

 cast iron, well scaled and heated till near- 

 ly infusion, was not at all affected by the 

 application of sulphur to its surface, not 

 even a mark being left. — A crucible was 

 made of cast iron, and some iron and 

 sulphur put into it; on applying heat the 

 iron and sulphur soon fused together, but 

 the cast iron underwent no change. 



Jinn, de Chirn. 



SOFT IRON THAT WILL CUT HARDENED 

 STEEL. 



Mr. Perkins has tried the experiment 

 with complete success, by placing a cir- 

 cular plate of soft iron, ^V o^ ^^ m(i\\ 

 thick in a lathe, and when it was made to 

 revolve with a speed equal to 10,000 

 feet of its circumference in a minute deep 

 incisions were made by the iron in a 

 common steel file. 



Here are 10,000 feet of the periphery of 

 the circular plate rubbed violently against 

 a portion of the file not exceeding -^- 

 of an inch where it touches. A clearer 

 idea will be afforded of the velocity and 

 consequent force with which the iron 



strikes against the file, by bringing the 

 10,000 feet into eighths of inches, which 

 makes 960,000, so that the steel receives 

 that number of rubs in a minute of time, 

 or 16,000 in a second of time, (producing 

 a heat which we should suppose to be 

 sufficient to fuse the steel,) the friction 

 on the file being unremitting; while the 

 friction upon the iron plate (supposing it 

 to be 8 inches in diameter,) was about 

 200 times less than that of the file, the 

 plate being cooled also in its passage 

 through the air at every revolution. 



Thus, then, it would appear that the 

 steel received perhaps 400 times more 

 heat than the iron, while it has not the 

 capacity to receive an equal quantity 

 without being melted. A proof of which 

 is perhaps afforded by what is called 

 "striking a light" with flint and steel. 

 By the collision, a portion of the steel 

 struck off is ignited and melted, while a 

 blow of equal force upon iron, with a 

 flint, will produce no effect. — Again, iron 

 retains its solid form at what is called a 

 welding heat — which is a degree of heat 

 at which steel passes into a fluid state. — ib. 



TO WHITEN IVORY THAT HAS BECOME 

 RED OR "FELLOW. 



Boil alum in pure water, so much as 

 will make it look white ; into this im- 

 merse your ivory, and let it remain in 

 an hour ; then rub the ivory with a cloth, 

 wipe it clean with wet linen rags and lay 

 theni in a moistened cloth to prevent 

 their drying too quickly, which causes 

 them to crack. ib. 



PHENOMENA OBSERVED IN PROVING THE 

 STRENGTH OF IRON BARS. 



It is interesting and important to note 

 the changes that iron undergoes in prov- 

 ing bolts or bars. It seems perfectly rigid 

 and unaffected by any force less than L 

 of its measure of strength, when a change 

 is indicated by small exfoliations, or 

 scales, from its surface. This is the con- 

 sequence of the bolt stretching, and ne- 

 cessarily lessening in diameter, and a 

 certain proof of its yielding is the pheno- 

 menon of its becoming sensibly warm : 

 the heat increases in the ratio of the 

 strain, and when the rupture takes place, 

 which is generally near the middle, it is 



