TRA.XSACTIOXS OF SECnOX G. 737 



obtained by th 3 Gas-engiaa Rasaarch Cotnuittee of the Institutioa of Meclianical 

 Engineers. A linear relation to connect specific heat and temperature was 

 employed, and the present case is a consideration, on somewhat similar lines, of 

 the results obtained in the classical experiments carried out by Dugald Clerk. 

 It is shown that with variable specific heat constants and cooling corrections 

 based on experimental data it is possible to account for tlie whole of the heat 

 liberated during explosive combination, and that it is unnecessary to assume the 

 existence of any after-burning. 



8. A Note on Gas-engine Explosions. By Professor J. Perry, F.R.S. 



9. The Direction and Velocity of Material-hearing Ocean Currents, loiih 

 Description uf an Ajjparatus recently designed for Estimating the same. 

 ByB.G. AllansDn-Winn, B.A., M.Inst.C.E.I. 



It appears that our present knowledge with respect to the action of bottom 

 currents is very incomplete ; and that experiments, conducted with great care over 

 lengthy periods, are necessary in order to establish certain data. 



A large number of experiments at many places would involve the expenditure 

 of considerable sums annually,, but the author is convinced that such an outlay 

 would be by no means thrown away ; and with the view of making a start with 

 actual experiments he has designed a simple form of current indicator by means of 

 which the direction and velocity of bottom currents may be very approximately 

 arrived at. 



The instrument exhibited is of simple construction, and not liable to get 

 out of order. It consists of a very heavily weighted vertical bar on which rotates a 

 free vane capable of being clamped the moment the apparatus leaves the bottom on 

 ■which it is resting during the registration of direction and velocity. A compass 

 is attached, and this is also clamped at the same moment ; so that the observer, on 

 pulling up the instrument, has been enabled to take the depth of water and the 

 direction of the bottom current. The measurement of the velocity i.<« arrived at 

 by the attachment to the vane of a current meter of approved pattern, such as 

 Revey's screw or B. T. Moore's.' 



This meter may be also set free on the instrument touching the bottom, and 

 clamped the moment it leaves the bottom. 



In order to guard against disturbances such as seaweed, jelly-fish, &c., &c., 

 the whole apparatus can be sunk in a cylindrical wire-netting case. Even this 

 protection is not sufficient ; so it is very advisable to take several soundings, and 

 then take the mean of these. 



The author feels that a great deal depends upon the simplicity of the working 

 parts of an instrument for sea observations, very delicate machines being liable to 

 be thrown out of gear by unavoidable rough usage and the action of salt water, 



' Pro:. Inst.C.E., xlv. 220. 



1902. 3 B 



