in the Twenty Years before 1895 39 



In the taking of serial temperatures and water specimens, 

 no time would have been saved by the use of wire, as with the 

 powerful steam-winch the sounding-line came up in perfect 

 safety from depths such as 1500 fathoms quite as quickly 

 as wire could have been brought up with great risk and with 

 the certainty of frequent loss. 



The thermometers used on board the " Challenger" were of 

 the Six type with protected bulb, the original Millar-Casella 

 . These thermometers did good service, and, like the hemp 

 sounding-line to which they were attached, their appreciation at 

 present is undeservedly low. In the Antarctic seas they were 

 found wanting, as it was known that they would be wherever the 

 temperature of the water did not fall with increasing depth. 

 But of the three years and six months that the cruise lasted, 

 three years and a quarter were spent in regions where this con- 

 :i is fulfilled. Their use, therefore, was amply justified, 

 and their convenience was great. 



In the instruments of the ordinary pattern, the graduation 

 was into single Fahrenheit degrees on glass slips fixed on the 

 vulcanite to which the thermometer was attached. After 

 the return of the "Challenger," I had them made for my own 

 use with a millimetre scale etched on the stem as well as the 

 Fahrenheit scale on the slips. As the length of a degree 

 Fahrenheit was 3 millimetres, it was easy to read accurately 

 to -fa Fahr. This is of great importance in the very deep 

 water, where the extreme variations of temperature are limited 

 ictions of a degree. In the survey of the Gulf of Guinea, 

 these thermometers gave very interesting results. When 

 trmperature observations came to be made in high latitudes 

 in winter and they are generally more instructive than those 

 in summer the conditions observed by the "Challenger" 

 in the Antarctic regions were found to be quite usual, and it 

 was Necessary to adapt the thermometer to the circumstances. 



With the Millar-Casella thermometer there was furnished 



a "pressure correction," to be applied to the readings in propor- 



lepth to which the thermometer had been sent. 



I always doubted the applicability of this correction, because 



I could not imagine tliat it had been determined in any other 



