24 ANNUAL OF SCIENTIFIC DISCOVERY. 



means whereby the great motive power might be safely applied to the 

 propelling of boats heavily loaded through the narrow channels of a 

 canal without producing such a commotion in the water as to seriously 

 injure the banks, or endanger the safety of the works. A boat built 

 after a plan patented by G. Parker, of Massachusetts, has been used to 

 some extent during the past summer, on the Delaware, Chesapeake, 

 and Raritan. canals, with good prospects of success in remedying the 

 evils above adverted to. It is a small boat, of about 100 tons burden, 

 with two engines, rated at 15 horse-power each. It differs from an 

 ordinary steam-boat in the peculiar shape of the wheel-buckets, and in 

 the addition of a float back of the wheel, which is in the centre of the 

 boat. The wheels are bent so as to form the segment of a circle, and 

 they enter and leave the water without creating the great motion 

 caused by the ordinary paddles. Should, however, the power required 

 cause any swell, the waters are smoothed down and pacified by the float 

 that follows the wheel. This float can be raised or lowered as circum- 

 stances may require. The average speed of the boat, when towing, is 

 represented to be four miles an hour, and the cost one half that of 

 horse-power. 



WATER AND STEAM PRESSURE GAUGE. 



MR. WILLIAM C. GRIMES, of Philadelphia, has recently invented an 

 instrument, which is intended to indicate continually the height of the 

 water, and pressure of the steam in a boiler, at any required place, at 

 whatever distance from the boiler. It consists of two metallic tubes, 

 which are inserted, the one into the steam space, the other into the 

 lower part of the water space of the boiler, and extend from the boiler 

 to the place at which the indications are required to be made, where 

 the ends of the tubes are brought side by side, and connected together 

 by a bent glass tube, one end of which enters each of the metallic tubes. 

 In the simplest form, (which is described for the purpose of explaining 

 more clearly the theory of the apparatus,) the tube connected with the 

 steam space (which may be called the upper tube) enters the boiler at 

 the water line, and runs for some distance horizontally, or a little inclined 

 downwards, when it again bends downwards for some inches, and then 

 runs in any convenient direction to the glass tube. The object of this 

 arrangement is to allow the steam to condense in this part of the tube, 

 and to keep the water which fills it always at the proper water-level of 

 the boiler. Each of the tubes is provided with a stop-cock near the 

 boiler, and on each of them, immediately below the glass tube, there 

 is a small hole, (called by Mr. Grimes the air-hole,) which may be 

 closed by a screw. In order to put the apparatus in working order, 

 the boiler is filled to above the water line, the stop-cocks of the tubes 

 being closed, and a small pressure of steam raised ; the stop-cocks of 

 the upper tube being then opened a little, the water will enter the tube, 

 and, expelling the air before it through the air-hole, will finally begin 

 to run through this hole ; the stop-cock of the upper tube is then closed, 

 and the plug of the air-hole screwed in. The lower tube is then filled 

 with water in a similar manner. The apparatus then contains water 

 in the metallic tubes, and air in the glass tube, or gauge. If now the 



