Physical investigations. 161 



work under the auspices of tlie Association, I have been chiefly 

 guided by these considerations, and the work has divided itself into 

 two separate investigations: — (1) The collection and discussion of 

 existing observations, especially those of surface temperature ; and 

 (2) An inquiry into the physical conditions obtaining in the English 

 Channel generally, and specially in the local fishing-grounds, by ob- 

 servations of temperature, examination of water samples, &c. 



Through the kindness of the Meteorological Council, access has 

 been obtained to all the records of surface temperature stored in the 

 Meteorological Office. Part of the material has already been handed 

 over to me, and a beginning has been made with its reduction and 

 discussion. This work is necessarily laborious, and some time must 

 elapse before any results can be presented for publication. 



The difficulties in the way of commencing practical work were 

 considerable. The steam launch belonging to the Association is use- 

 less for sounding outside the harbour except under unusually favour- 

 able conditions. I accordingly made an application to the Govern- 

 ment Grant Committee of the Royal Society for the sum of £100, to 

 pay hires of steam tugs for trips across the Channel at intervals. 

 This application was granted. The unusually bad weather of the past 

 summer, and the comparatively small amount of time at my disposal 

 for research, have unfortunately prevented more than one trip being 

 made, the results of which are given below. 



The methods of marine physical investigation are now sufficiently 

 well known to make it unnecessary to describe in detail the instruments 

 and apparatus used. Temperature observations are made with 

 Negretti and Zambra's reversing thermometer, in the Scottish 

 frame,* and samples collected by Mill's self-locking water-bottle. t 

 Where surface observations only are made, a sample of water is 

 obtained in a wooden bucket, the temperature being taken by means 

 of an ordinary thermometer, and the sample transferred to a glass 

 bottle. All thermometers used have been verified by repeated 

 comparison with a Kew standard belonging to the Association, and 

 in most cases the instruments have Kew certificates in addition. 

 Every care has been taken throughout to keep the errors of tempera- 

 ture observations within 0"1° F. 



As the samples collected are at once brought to the Laboratory 

 and their examination proceeded with, it has not been thought neces- 

 sary to take special precautions in sealing the bottles. Winchester 

 quarts of the ordinary type are used, note being made that the 

 stoppers are well ground in each case. 



Determinations of density have been made in the first place with 



* Proc. Roy. Soc. Edin., xii, p. 928. 



t Mill, ibid., 1886, vol. xiii, pp. 539—546. 



