i8 THE DEPTHS OF THE SEA 



invented by the Rev. Stephen Hales, D.D., of Corpus 

 Christi College, Cambridge, the friend of Pope, and 

 perpetual curate at Teddington Church. Dr. Hales 

 was a man of many inventions, and, amongst others, 

 he is said to have suggested the use of the inverted 

 cup placed in the centre of a fruit -pie in which the 

 juice accumulates as the pie cools. His device of the 

 closed bucket with two connected valves was the 

 forerunner of the numerous contrivances which have 

 since been used for bringing up sea-water from great 

 depths. 



These were amongst the first efforts made to obtain 

 a knowledge of deep-sea temperatures. About the 

 same time experiments were being made by Bouguer 

 and others on the transparency of sea-water. It was 

 soon recognized that this factor varies in different 

 seas; and an early estimate of the depth of average 

 sea-water sufficient to cut off all light placed it at 656 

 feet. The colour of the sea and its salinity were also 

 receiving attention, notably at the hands of the dis- 

 tinguished chemist Robert Boyle, and of the Italian, 

 Marsigli, mentioned above. To the latter, and to 

 Donati, a fellow-countryman, is due the honour of 

 first using the dredge for purposes of scientific inquiry. 

 They employed the ordinary oyster-dredge of the local 

 fishermen to obtain animals from the bottom. 



The invention of the self-registering thermometer 

 by Cavendish, in 1757, provided another instrument 

 essential to the investigation of the condition of things 

 at great depths ; and it was used in Lord Mulgrave's 

 expedition to the Arctic Sea in 1773. On this voyage 

 attempts at deep-sea soundings were made, and a 

 depth of 683 fathoms was registered. During Sir 

 James Ross's Antarctic Expedition (1839- 1843) the 

 temperature of the water was constantly observed to 

 depths of 2,000 fathoms. His uncle. Sir John Ross, 

 had twenty years previously, on his voyage to Baffin's 



