TEMPERATURE OBSERVATIONS IN LOCH EARN. 743 



water-tight by means of a rubber sleeve connecting the projecting part of the 

 clockwork to the water-tight case. The arrangement may be understood from a 

 study of the photograph in fig. 1. 



At the commencement some difficulty was experienced in making the clock case 

 water-tight. This difficulty was overcome by cementing the large joints with marine 

 glue, but the admission of water had allowed some of the clock parts to rust, which 

 caused an unfortunate stoppage at a rather critical time. On the whole, however, 

 the instrument worked well, and, with the experience gained in its manufacture, it 

 will be possible to design a reliable thermograph for the measurement of temperature 

 under water. 



Fio. 1. — Thermograph. 



The instrument was calibrated in the Physical Laboratory of the University of 

 Edinburgh by Mr Young and Mr M'Ewen by immersion in a water bath. A 

 difference in temperature of 1° C. caused a scale deflection of 3 '4 mm. An instrument 

 with a more open scale would have been an advantage, but the thermograph used 

 had been designed for ordinary atmospheric work. As it • was, some extremely 

 interesting records were obtained and will be referred to later. 



Current- Meter. — The current-meter referred to was of a completely new design, 

 and was constructed by Mr A. H. Baird from drawings prepared by him on sugges- 

 tions and directions given by Mr Wedderburn. Current-meters hitherto in use 

 have only been capable of recording the horizontal component of currents, and for 

 most purposes, e.g. the measurement of the flow of rivers and the strength of tidal 

 currents in the ocean, this is sufficient. The currents in inland lakes are so slow 

 that the usual type of current-meter is not suitable. Moreover, it was suspected that 

 at least towards the end of lakes currents would have appreciable vertical components, 



