742 DR E. M. WEDDERBURN AND MR A. W. YOUNG ON 



A new type of thermograph and a current-meter designed to measure vertical as 

 well as horizontal currents were employed. 



Thermograph. — -Two forms of recording thermometers have hitherto been used 

 for measuring temperatures at considerable depths below the surface of water, 

 (l) A platinum* thermometer with Callendar recorder was used in Loch Ness with 

 some success, but it was out of the question to use so elaborate a means of measure- 

 ment for observations limited in duration to one month, partly on account of expense, 

 and partly on account of the time which would have been required to put the 

 instrument in proper adjustment. (2) Dr F. M. Exner used an ordinary Richard 

 thermograph in the Wolfgangsee.f The whole instrument was protected from the 

 action of water by being enclosed in a heavy water-tight metal box, and was 

 accordingly very sluggish and quite unsuitable for the observation of rapid 

 temperature changes. 



The new thermograph consisted of the usual form of metallic thermometer 

 supplied by Messrs Short & Mason for use in air, with a special clock and recording 

 gear supplied and largely designed by Messrs J. Ritchie & Sons, Edinburgh. The 

 registering portion of the thermograph was not protected from the water in any 

 way, and therefore the lag of the instrument was negligible. The arm of the 

 thermograph was made to press against the recording drum at intervals of \ min., 

 1 min., 2 min., or 4 min., according as the drum was made to revolve in 3, 6, 12, or 

 24 hours. A prick-mark on the drum registered the temperature at the moment 

 of contact, and the distance between successive prick-marks was '05 inch or 

 1"27 mm. On the drum was placed a sheet of fine millboard, as Mr Ritchie found 

 this to be most suitable after numerous experiments with waxed papers and other 

 substances. Interposed between the metal drum and the millboard was a rubber 

 sheet, and when the instrument was in proper adjustment an excellent record was 

 obtained. The records were taken on plain unruled paper, and for the purpose of 

 reading them a scale was drawn on tracing paper, after the style of an ordinary 

 printed thermograph record form, with parallel lines for each degree Cent., and 

 parallel arcs of circles marking intervals of time. With this scale the temperature 

 could be read to within '1° C. 



The recording drum was an ingenious arrangement designed by Mr James Ritchie. 

 The clockwork which drove the drum and pressed the arm of the thermograph against 

 it was encased in a water-tight metal box, and water-tight metal screw plugs gave 

 access for winding the clockwork and for altering the rate of the drum. The drum 

 was driven by a rocking movement which, while pressing the thermograph arm 

 against it, gave the drum a forward impulse, so that the drum moved round in a 

 series of jerks given periodically. The junction between the clockwork and the 

 mechanism which gave the impulse to the thermograph arm and drum was made 



* "The Temperature of the Fresh-water Lochs of Scotland," Trans. Roy. Soc. Edm., vol. xlv, p. 410. 

 t Sitzber. der K. Akud. d. Wiss. in Wien, math.-nat. Kl., Abt. ii a, January and December 1908. 



