MECHANICS AND USEFUL ARTS. 89 



case, between two heads provided with suitable packing, and attached to a 

 rod, by which arrangement the charge is prevented from "blowing out," or 

 obtaining vent in the direction of the line of the hole in which the tube and 

 charge are placed, and the whole effect of the charge is exerted against the 

 sides of the tube or case. 



By this method rocks may be blasted with much greater facility than by the 

 ordinary mode, no^ tampering or packing of clay being necessary to confine 

 the powder within the hole. The implement may be used repeatedly, as it 

 can not be projected to any great distance from the spot where used. 



The Northern Star, of Warren, R. I., contains a notice of the operation of 

 this improvement witnessed by five persons, by which one pound of powder 

 moved one hundred tons of rock. 



BROWN'S PATENT SOUNDING INSTRUMENT. 



This invention by Captain C. F. Brown of Warren, E. I., delates to a new 

 and useful instrument for sounding the ocean depths, and consists in attaching 

 to a spindle a long spheroidal chamber, containing some gunpowder within 

 the lower part, and having underneath the chamber a needle operated by a 

 spring, which is forced against a percussion cap on a nipple, and thereby 

 igniting the charge of powder when the lower end of the spindle strikes the 

 bottom ; and the time that elapses from the period the instrument is dropped 

 until the sound is heard, or concussion felt, is noted, and the depth deter- 

 mined upon positive data to form proper conclusions. The sound of the 

 explosion will be heard or the concussion will be felt, at the surface of the 

 ocean, by those who have let down the instrument, and the time which 

 elapses between letting it fall and hearing the sound of the explosion must bo 

 ascertained by a stop-watch. By this means the depth of the ocean may be 

 ascertained, for a table may be formed from a number of recorded experiments 

 giving the time between the dropping of the instrument, and that when the 

 sound is heard at the surface, according to ascertained depths. A percussion 

 cap can be used on the nipple, or a pill of an aUoy of potassium. Water is 

 required to ignite the latter, and for this purpose small apertures are left at 

 the upper part of the tube, to be opened when the instrument strikes the 

 bottom. 



This instrument is a simple means for sounding the depth of old ocean, and 

 also for ascertaining the strength and direction of a current, for if it appears 

 that the ocean is agitated at a spot on the surface distant froln where the 

 instrument was dropped, it will afford evidence of a current, and its velocity 

 according to that distance. Scientific American. 



IMPROVED COAL-HOLE COVER. 



*- 



Mr. F. H. Moore of Boston, has recently patented a rather singular im- 

 provement on the covers of the ordinary coal-hole in our sidewalks, designed 

 to prevent the possibility of accidents, either from children falling through 

 them when left open for a few minutes or from pedestrians stumbling over 

 them when loosely fixed. Moore's cover is not exactly removable and only 



