36 A Retrospect in Oceanography 



stations. The work at a station generally took the whole 

 day from sunrise to sunset, and every one familiar with steamers 

 knows how expensive in coal is the operation of keeping station. 



The material collected at each station had to be examined, 

 preserved and stored, before the ship arrived at the next one. 

 The stations were generally about 200 miles apart, so that in 

 the passage from one port to another a station was made 

 every second or third day. This was easily accomplished under 

 sail and it added enormously to the comfort and the interest 

 of the voyage. All the advantages of having a wooden sailing 

 ship were not fully realised at the time. It was not until 

 I had taken part in one or two expeditions in well found iron 

 or steel ships in tropical waters that I found out the discomfort 

 which we escaped by being on board of an "old wooden ship." 

 The temperature of the air in the ship was, of course, never 

 lower than that of the air outside; but, on the other hand, 

 it was never higher. Nothing astonished me more than the 

 perfect uniformity of temperature of the air of the main deck 

 of the ship in the tropics. I was able to make experiments 

 on the effects of pressure on the deep sea thermometers in a 

 hydraulic apparatus on the main deck, which I could not have 

 made anywhere else. The temperature of the air did not 

 vary by one-tenth of a degree (C.) during the whole of 

 the day. 



Iron or steel ships, even the magnificent yacht of the Prince 

 of Monaco, get heated through by the sun in the course of the 

 day, and at first they do not cool as much during the night. 

 They are like a black bulb thermometer, they do not lose 

 as much heat as they gain until their temperature has risen 

 a good many degrees above the mean temperature of the air, 

 and that can be pretty high. 



The voyage of the "Challenger" lasted three years and five 

 months. Of this time three years were spent between the 

 parallels of 40 S. and -40 N., and the greater part of that 

 time between the tropics. I have no hesitation in saying that 

 the work could not have been carried on continuously in these 

 tropical seas for such a length of time in any other kind of 

 ship. The principal points of advantage were, the thick wooden 



