52 THE VOYAGE OF H.M.S. CHALLENGER. 



" In the case of india-rubber the rise of temperature was found to be about 1°"3 F. 

 for each ton-weight of pressure per srpiare inch ; and the fall in relaxation was almost 

 exactly the same. 



" With cork each additional ton of pressure gave less rise of temperature than the 

 preceding ton ; and the fall on relaxation of pressure was, for one or two tons, only 

 about half the rise. For higher pressures its ratio to the rise became greater. Two 

 tons gave a rise of about 1°'6 F., and a fall of 0°"9 F. 



" With the same arrangement, the fall of temperature in water suddenly relieved 

 from pressure at a temperature of 60° F. was found to be for 



One ton-weight per square inch, . . . . . 0° - 25 F. 



Two „ „ ..... 0°-56 „ 



Three „ „ ..... 0°-93 „ 



Four „ „ ..... l°-35 „ 



" These numbers give the averages of groups of fairly concordant results. I 

 employed cooling exclusively in these experiments, because one of the valves of my pump 

 was out of order, and the pressure could not be raised at a uniform rate. The effects 

 obtained for successive tons of pressure are thus, roughly, o, 25, 0° - 31, 0°"37, and 0°"42 F. 



" If these results may be trusted, they probably indicate a lowering of the 

 maximum-density point of water by pressure." ' 



In the next extract it will be seen that I deduced from these data a lowering of 

 the maximum-density point amounting to about 3° C. per ton. 



The experiments on water were carried further in the following year by Professors 



Marshall and Michie Smith, and Mr. Omond. 2 The second of their papers contains the 

 annexed graphic representation of the results, which is alluded to in the following extract. 

 1 [See footnote to p. 27.] 2 Proc. Roy. Soc. Eclln., voL xl. pp. G26 and 809, 1882. 



