22 THE ATLANTIC. [ CHAP. I. 
that due to heat, the amount of excess depending upon the 
thickness and uniformity of the glass of the bulb. On our 
return, the late Professor W. A. Miller devised a plan of de- 
fending the bulb from external pressure by inclosing it in an 
outer shell of glass, with fluid and a bell of vapor between. 
With this construction the outer wall bears the whole of the 
pressure, compressing in turn the included bell of vapor and 
relieving entirely the inclosed thermometer bulb. This ‘* Mil- 
ler-Casella” modification of Six’s registering thermometer has 
given to deep-sea temperature determinations the element of 
accuracy previously unfortunately wanting. 
Public interest was now fairly aroused in the new field of 
research. The rapid development of ocean telegraphic com- 
munication made all these results which affected telegraphy in 
any way—the precise depth, the nature and composition of the 
bottom, the presence or absence of animals capable of making 
inroads into hemp or gutta-percha, the temperature of the wa- 
ter through which telegraph cables might have to pass—of the 
highest practical value; while the novelty and peculiarity of 
many of the observations awakened a wide-spread curiosity and 
interest in even the purely scientific bearings of the inquiry. 
Our cousins across the Atlantic had been working along with 
us part passu, and ere long several of the European States sent 
out deep-sea expeditions more or less effective. None of these 
were attended with any great amount of success, and it seemed 
evident that England must give, at all events, the first broad 
outline of the physical conditions of the bed of the ocean. 
How this was best to be done was a matter of the most serious 
consideration and frequent consultation among those to whom 
the earlier stages of the inquiry had been intrusted ; and finally 
Dr. Carpenter addressed a letter to the First Lord of the Ad- 
miralty, urging the dispatch of a circumnavigating expedition 
thoroughly equipped, and with a competent scientific staff, to 
traverse the great ocean basins and prepare sections showing 
