90 ANNUAL OF SCIENTIFIC DISCOVERY. 



to a limited degree liftable. The upper surface resembles the ones now in 

 general use, but its under surface is armed with three vertical rods which 

 descend through ears in the sides of the seat. The cover is provided with a 

 ring let into its top to form a convenient handle, and the hole is opened by 

 raising the cover bodily to a height of about three feet, in which position it is 

 sustained by a catch or a spring, and the coal or wood is to be thrust hi side- 

 wise between the three rods. The coal-hole, when open, resembles a half- 

 constructed parrot-cage, an embellishment which may not be considered par- 

 ticularly ornamental in front of a city mansion, but is decidedly more so than 



the very undesirable pits and foot-traps now exhibited. 



i 



IMPROVEMENTS IN AMALGAMATORS. 



An unproved amalgamator patented by Samuel Gardiner, Jr., of New York, 

 consists of one or^more parrs of metallic rollers geared together and revolving 

 in a trough in contact with mercury. The journals of the rollers are hollow, 

 and so are the rollers themselves; the latter are perforated with fine holes, so 

 that, by the introduction of water through the journals, there will be an un- 

 ceasing outward discharge of water on the surface of the rollers, keeping them 

 continually moist. The quartz previously pulverized and mixed with water 

 into a thin paste, is introduced from above upon the rollers, and by them 

 spread over their entire surfaces ; the rollers coat themselves, as they revolve, 

 with mercury, and the latter absorbs the gold dust from the paste. The 

 issuing water from the rollers loosens the quartz as fast as it forms upon their 

 surfaces, and the gold, being heaviest, falls to the bottom of the trough. A 

 running stream of water constantly flowing into the trough carries away the 

 quartz dust, and the rollers come round with a fresh coating of mercury at 

 every turn. 



PRESSURE STOPPER FOR CHAIN CABLES. 



This improvement by James Emerson of "Worcester, Mass., consists in a 

 means of preventing the injurious effects resulting from, the sudden jerking of 

 the anchor chain, when a vessel is riding at her moorings. In rough weather 

 and a heavy sea, the windlass is liable to be injured, and the chain to be 

 snapped, from the cause above-mentioned. Mr. Emerson makes use of a 

 stopper, one portion thereof consisting of a sliding weight under which the 

 chain passes. * The weight is pressed down upon the chain by means of a 

 lever, so that the degree of pressure may be very easily regulated. "When the 

 force of the jerk exceeds the pressure of the stopper, the chain will slip a little, 

 and so afford the required relief. 



WHAT IS A LANCASTER GUN? 



The invention of Mr. Lancaster relates wholly to the contour of the gun's 

 bore, which is a modification of the common rifle bore. Instead of cutting 

 twisted or helical rectangular grooves in the bored surface, as in all ordin- 

 arily rifled arms, Mr. Lancaster forms his bore in the shape of a twisted 



