20,360. Kent. W. G., and Hodgson J. L. Sept. 28. [Cognate Application No. 9976, A.D. 1909, dated April 27.] Current meters; anemometers; thermometers.-In Venturi or like meters, the flow is measured by obtaining a movement proportional to the logarithm of the flow by adding together movements proportional to the logarithms of functions of the variables on which the flow depends. The flow can also be obtained by adding to the logarithm of the flow under standard conditions, the logarithms of functions of the variables, or by obtaining a movement proportional to the sum of the logarithms of functions of the velocity and density. An inverted bell IB and float SF, Fig. 4, so shaped that the change in buoyancy can be made to follow any law, can be used to give movements proportional to the logarithms of the pressure or the Venturi head. The head can also be measured by means of the difference in height, in liquid in two arms of a U- tube, and the pressure, which may be measured against a vacuum, can be measured by a piston, or either can be measured by means of a Bourdon gauge. The resulting movements can be so resisted by springs &c. or modified by cams, a system of links &c., that the movements transmitted to the counting-mechanism are proportional to logarithms of functions of these quantities. The temperature may be measured by the expansion of a rod or mercury in a tube in the main or by means of a vapour-pressure thermometer as shown in Fig. 12, which illustrates a thermometer having a steel or like shell t containing acetone &c. and a thin tube t<1> filled with a liquid having a low vapour pressure, said tube leading to the pressure gauge. A bell and float can be used as before to obtain a movement proportional to the logarithm of a function of the temperature. The mechanism used for adding the movements obtained in these ways is shown in Figs. 1 and 2 and comprises a pair of bevel-wheels a, a<1> driving the spindle b<1> of an intermediate wheel b at an angular rate equal to half the sum of their rates, this spindle driving a wheel c which coacts with a further wheel c<1> to drive a second intermediate wheel d and spindle in the same way. The angular velocity of this last wheel d is therefore equal to the sum of half the angular velocity of the wheel c<1> and a quarter of the sum of those of the wheels a, a<1>. The wheel d is connected to a calculated cam L, against which is pressed a feeler on an arm F on which is mounted a sector F' engaging a pinion S' on a hollow shaft S loose on the spindle D<1> of the counting-mechanism, which is driven by the engagement of the pawl B with the wheel D fast on the spindle D<1>. The pawl is carried on an arm A on a hollow continuously-rotated shaft M and is lowered into driving position by the engagement of an arm B' on it with a pallet S3 on the shaft S, the position of the pallet which depends on the amount of movement derived from the cam L, deciding the length of time the pawl is driving the wheel D during each revolution of the shaft M, a stop B<1> being arranged to contact with the arm B<2> and throw the pawl out of engagement at a certain point of its travel. A system of pulleys may be used instead of the gear-wheels a, a<1>, &c. to get the summational movement. To minimize leakage of gas &c. during the measuring operation glands can be used in which either the escaping fluid is subjected to wire drawing or in which a bell dipping in a mercury seal is employed. To measure pressures &c. too small to be easily read with the ordinary arrangement, Venturi tubes can be fitted in a by-pass to the main flow tube, means being provided for shutting off the flow in the main tube and throwing in other gearing when these finer readings are required. By the use of leaky valves in the pressure-measuring devices, pulsation can be corrected for, the gas may be dried before measurements are taken, and the pipes leading from the Venturi tubes to the measuring-apparatus are laid horizontal to obtain the same head of condensed water in each when measuring steam pressures.