MECHANICS AND USEFUL ARTS. 83 



hour. Each machine uses thirty gallons of water per minute, at 

 about three lumdred pounds pressure, according to the hardness of 

 the substance to be acted upon. The machine, when in operation, 

 fixes itself dead fast upon the rails during the cutting strike, and 

 releases itself at the back or return stroke, and traverses forwards 

 the requisite amount for the next cut without any manual laljor. 

 No percussive action results from the machine, either against 

 the roof or into the coal, but simply a concentrated pressure, pro- 

 ducing a stead}" recijirocating motion, at fifteen strokes per minute. 

 There is, consequently, no dust nor noise, and little wear and 

 tear. For the same reason, when cutting pyrites, the tools throw 

 out no sjjarks, and the Avorkmen can hear any movement in the 

 coal or roof. The price of a machine, a working model of which 

 is at the Industrial Exhibition, is stated to be £125. 



STEAM FIRE-PROOF SAFE. 



Rev. Rufus S. Sanborn, of Wisconsin, exhibited to the Massa- 

 chusetts Institute of Technology, in December, 1866, and described 

 a model of a steam fire-proof safe, of his invention. The nature 

 of this invention consists in placing one or more boxes, or unfilled 

 safes, one within the otlier, the outside case being filled or othei-- 

 wise in the ordinary way, and these inner boxes detached from 

 one another and the outside case by means of flanges or spurs, so 

 as to form air-chambers all around said inside box or boxes, and 

 into these air-chaml)ers are inserted metallic vessels for holding 

 water, with simple steam-valves, which will be Oj^ened so as to 

 allorw the steam to escape when the heat of the inside of the safe 

 shall become sulficient for that jjurpose. 



This steam saturates the air-chambers, and its surplus escapes 

 by the doors, so as to keep the tempei'ature of the inside of the 

 safe about that of boiling water, in which temperature none of the 

 papei-s of the inside box can either burn or char so long as any 

 steam can be maintained. 



By a peculiar arrangement of a succession of these vessels, one 

 exhausts after another, and thus for a long time there is the most 

 complete protection, in addition to the other protection which the 

 filling and air-chambers aflbrd. He gave a history of the experi- 

 ments which had led to the above result, and stated that the safe 

 was soon to have a public trial. In an ordinary-sized safe, the 

 moist filling would save an hour in absorbing heat before the heat 

 could penetrate to the interior. Such a safe would hold fifteen 

 gallons of water, which, under the arrangement described, would 

 take a very long time for the entire escape of the steam. 



At a trial held soon afterward, this safe was submitted to a heat 

 so intense as to melt the knobs on the door, and was kept exter- 

 nally red hot for nearly four hours : papers in the interior were 

 taken out entirely uninjured, and only a gill of water vaporized ; 

 while those in a safe by one of the best makers, submitted to the 

 same trial, were badly charred, as well as the whole interior wood- 

 work, and in another hour would have been destroyed. 



