42 A Retrospect of Oceanography 



from the bottom to 250 fathoms above it (Scottish Geographical 

 Magazine, 1888, p. 13). This is a branch of inquiry which 

 has received very little attention, but it deserves to be 

 assiduously cultivated. We have many determinations of 

 distribution of deep-sea temperatures, but we may say no- 

 discussion of them from a calorimetric point of view. In the 

 Proceedings of the Royal Society of Edinburgh, 1885-1886, 

 p. 423, I discussed a series of observations made at different 

 dates in Loch Lomond from this point of view, giving the 

 heat exchanges which take place in the course of the year. 

 The heat-unit used in this discussion was the fathom-degree 

 (Fahr.) that is, a depth of I fathom heated one degree (Fahr.). 

 If the fathom has a sectional area such that the volume of 

 water weighs I pound, then the fathom-degree is the same 

 as the ordinary British heat unit, the water-pound-degree. 

 It is rather remarkable that, if the metre be used for measuring 

 depth, and the Centigrade degree for measuring temperature, 

 the resulting heat-unit for depth is the same as when the fathom 

 and the Fahrenheit degree are used, because the fathom is 

 1-8 times the length of the metre, and the Centigrade degree 

 is 1-8 times that of the Fahrenheit degree. 



The record of the "Challenger" in freedom from accidents 

 is a very brilliant one. She was supplied with two qualities 

 of sounding line designated Nos. I and 2, of which No. 2 was 

 inferior in size and quality. It was used during the first 

 two months of the cruise and was found so untrustworthy 

 that it was condemned, and from February 1873 line No. i 

 was used exclusively. Before reaching Lisbon three No. 2 

 lines were lost, with three thermometers. After leaving 

 Lisbon the No. 2 line was used for the last time on February 19, 

 1873, when it parted, and two thermometers were lost. From 

 this date until the end of the voyage in May 1876, No. i line 

 was used exclusively, and it parted on five occasions, namely, 

 April 28, 1873, losing one thermometer; on May i, 1873, 

 losing one thermometer; on August 16, 1873, losing two 

 thermometers ; and on June 14 and June 16, 1874, losing on each 

 of these days two thermometers. After June 16, 1874, no 

 sounding-line was lost. In all, therefore, nine sounding-lines 



