TRANSACTIONS OF SECTION G. 775 



Method of Workiiuj. — When required to prepare soundings or sections for any 

 hydraulic work — say fifty or one hundred miles of proposed river conservancy works 

 — to a depth varying from eight to lifteen feet below the surface of the water, it ia 

 merely necessary to attach fifteen feet of a rough metal or other sounding bar 

 to the central axle, by a thumbscrew, leaving about two feet of the sounding bar 

 above the central axle, working in front of and pointing to the dial, placed at the 

 side of the observer, when sitting in the stern of the boat, to note the dial-readings, 

 ■when necessary, in his notebook. 



On the boat being set in motion, the sounding bar (contrary to expectation) will 

 remain hanging in the vertical position, until it meets with some obstruction or rise 

 in the ground, when the sounding bar, working round the central axle, will be 

 pushed from a vertical into a slanting position, and according as its end under water, 

 resting on the ground, is raised from fitteen to less depths below the surface of the 

 water, say to ten, five, and two feet, the other shorter end of the sounding bar 

 will point to ten, live, and two feet on the dial. If any greater obstruction raises 

 the lower end of the sounding bar to the surface of the water, then its upper end 

 will point to zero on the dial. 



A horizontal roll of ' section paper ' is placed at back of the dial or elsewhere, 

 kept in motion at a given rate by a simple arrangement of clockwork, or by float- 

 boards or a screw worked by the resistance of the water when the boat is rowed or 

 otherwise set in motion. 



On the section paper is marked to scale a perfect contour line, representing the 

 surface of the ground below water, by a pencil pointer or pen attached to the 

 central axle, which latter is kept in motion by the rise and fall of the sounding bar 

 firmly screwed to it. 



The author, however, states that the section paper may be frequently dispensed 

 with, and the character of the surface of the ground accurately defined by the 

 action of the instrument under water, as more fully described in his paper. The 

 instrument is designed to enable the observer to enter all necessary information in 

 his notebook, three or more scales being marked on the semicircidar dial, to suit 

 sounding bars ten, twenty, or more feet in length. 



3. On the Economical Effect of using Cheap Oasfor Gas-motors, with a descrip. 

 Hon of Apparatus for producing such Gas. By J. Emeeson Dowson, C.E. 



After describing what had been done by other inventors, the author 

 gave the following particulars of his apparatus: — The retort or generator 

 consists of a vertical cylindrical iron casing which encloses a thick lining 

 of ganister, as in a foundry cupola, to prevent loss of heat and oxidation of 

 the metal, and at the bottom of this cylinder is a grate on which a fire is built 

 up. Under the grate is a closed chamber, and a jet of superheated steam 

 plays into this and carries with it by induction a continuous current of air. The 

 pressure of the steam forces the mixture of steam and air upwards through the 

 nre, so that the combustion of the fuel is maintained while a continuous current of 

 steam is decomposed, and in this way the working of the genei'ator is constantj and 

 the gas is produced without fluctuations in quality. The steam is produced and 

 superheated in a zigzag coil heated by gas. The nature of the fuel required 

 depends on the purpose for which the gas is used. If for heating boilers, fm-naces, 

 &c., coke or any kind of coal may be used ; but for gas-engines, or any application 

 of the gas requiring great cleanliness and freedom from sulphur and ammonia, it is 

 best to use anthracite, as this does not yield condensable vapours and is very free 

 from impurities. To produce 1,000 c. ft. only 12 lb. of anthracite are required (allow- 

 ing 8 to 10% for impurities and waste) and about 7 pints of water. The cost of 

 making the gas depends to a certain extent on the size of the generator. Experience 

 with 16 generators has shown that the three sizes in use, producing respectively 

 1,000, 1,500, and 2,500 c. ft. per hour, make gas at a cost of 4^c?., Zyi., and 2\d. per 

 1,000 c. ft. (including repairs, depreciation, and interest on capital outlay). Ap- 

 proximately the composition of the gas thus made is : Hydrogen 20%, carbon 



