252 



NA TURE 



[August 19, 1922 



departures from the declared calorific value are strictly 

 comparable, being represented by equal displacements 

 of the recording point, whatever the declared calorific 

 value. 



The water doled out passes through a small hole 

 into a second compartment of the water-box, and thence 

 to the calorimeter proper. When the bucket is over- 

 turned, the jet of water misses the bucket and enters 

 a third compartment of the water-box, whence it 

 passes to a fourth compartment, to be delivered to a 

 small celluloid water-wheel, which drives, through an 

 elastic connection, the escapement of a one-wheel 

 pendulum clock ticking half-seconds, and through an 

 intervening mechanism — called by Prof. Boys the 

 " thinking machine " — the axle of the gas meter. 



The Gas Meter. — The gas meter is shown in vertical 

 section in Fig. 2, the smallest arrow indicating the 

 direction of entry of gas previously saturated with water 

 vapour. The meter drum is of celluloid, and is provided 

 with buoyancy chambers A, so that the drum is largely 

 carried by the water and not by the axle. The gas 

 measured in any compartment is therefore contained 



in a chamber of which the sides, ends, roof, and about 

 two-thirds of the floor are independent of the water- 

 level, which can be adjusted to T „ Jo^tli inch by refer- 

 ence to the upturned points, B. Changes of water- 

 level, even if they should occur, would clearly have 

 little effect on the capacity of the meter. The meter 

 drum rests loosely on the axle, which is screwed, so 

 that if meter and axle turn at the same rate there is 

 no endlong movement of the drum. The axle works in 

 a long sleeve, C, screwed into a brass ring, and vaseline 

 is forced in to make axle and sleeve water-tight. No 

 stuffing boxes are employed, and the inlet and outlet 

 aprons of the usual wet-meter drum are replaced by 

 discs closing the front and back of the usual four 

 compartments. The meter is enclosed gas-tight 

 within a glass bell D above, and a spun copper bowl, 

 E, below. The pressure in the meter is about J inch 

 of water in excess of atmospheric, such excess being 

 due to the inclusion in the gas circuit of a pin-hole 

 burner to prevent the calorimeter burner being extin- 

 guished by the sudden slamming to of a door, etc. 



The " Thinking Machine." — This device, already 

 referred to, is shown in plan in Fig. 3A. It consists 

 of a small ball-disc-cylinder integrator, a vertical 

 section of which is shown in Fig. 3B, coupled with 

 epicyclic double reduction gear, as shown at A in Fig. 

 3A, inserted between the clock and the meter axle so 

 as to control the rate of revolution of the meter drum. 



NO. 2755, VOL. I 10] 



The epicyclic device gears down the motion of the 

 disc of the integrator in the ratio 3 : 2, the disc itself 

 being geared down from the water-wheel in the ratio 

 4:1. The motion of the cylinder of the integrator is 

 geared down in the ratio 15 : 1. 



Temperature and pressure corrections to the gas 

 volume are automatically and positively effected in 

 the following way. It is clear that if the ball, B 

 (Fig. 3B), makes contact with the rotating disc, C, 



X 



exactly at the centre of the disc, no rotary motion 

 will lie communicated by the disc to the ball and 

 consequently none to the cylinder D. Such a position 

 of the ball corresponds to normal conditions of 

 temperature (6o° F.) and pressure (30 ins. of mercury) 

 of the gas, and may be conveniently referred to as its 

 N.T.P. position. The radial displacement of the ball 

 from the centre of the disc is made to depend upon 

 atmospheric temperature and pressure as follows : E 

 (Fig. 3A) shows in plan a glass bell filled with air floating 



in a mercury and water seal, and connected by a lever 

 system with a fork which displaces the ball to one side 

 or other of the centre of the disc, according as the bell 

 rises or falls with change of atmospheric conditions. 

 The lever system is such that the ball moves 1 inch, 

 equal to the radius of the cylinder, when the gas 

 volume correction is 10 per cent. Such displacement 

 of the ball is accompanied by its rotation, producing 

 rotation of the cylinder, D, whereby endlong motion 

 is communicated to the meter drum, resulting in the 

 gas inlet to the meter, F, Fig. 2, being further closed 

 or opened as required, so that the rate of gas delivery 



