On the Compressibility of Solids 389 



production of considerable tension in that part of the glass. 



\ ithstanding my directions, some of the tubes were rounded 

 off in the lamp and the effect was as I had foreseen. The only 

 one of these ends which I used burst. In the case of ends 

 which have been cut off and not heated, the fracture is confined 

 to the part of the tube outside the apparatus. In the case of 

 the end with rounded edges the outside part was fractured in 

 the ordinary way. and in addition the rounded portion, which 



e: x posed to no difference of pressure, exploded out of 

 sympathy, much after the fashion of a Prince Rupert's drop. 



Postscript. For the purpose of the report on the results of 

 the "Challenger" Expedition, the general thermometric work 

 I to Professor Tait of Edinburgh. 



In the course of his examination of the thermometers them- 

 selves, he felt the necessity of a knowledge of the absolute com- 

 pressibility of the glass used in their construction, and he came 

 to me and asked me if I would lend him my apparatus for thi-i 

 purpose. 



In making this request he stated to me that, before doing 



he had examined every other instrumental method which 

 claimed to furnish by direct observation the absolute compres- 

 sibility of solid-, and had found them either faulty in design, or 

 so defective mechanically as to shake hU confidence in the 

 value df tin- result- which he would obtain by their use. With 

 regard to my instrument, he acknowledged that the principle 

 of it was sound, that the mechanical expression of it was suc- 



:il. and that the re-ult- obtained with it. 1>\ competent 

 observers HUM !> tni-tworthv. 



I was naturally much ^ratified ! ilmtc 



6 excrllriic. .pparatll- i'V "lie of the Illo-t dl 



1 1. 1 id I v necessan I 



nment \\ without d.-l..\ t.. the l'h\ 



Laborato: e Kdinlmru'h I'nivei-itv. when- it remained 



until the with the "Ch.tll- 



The account of thi^ | 1- f.-und in Professor '1 



t in the M'cnnd volume <.f th' I Phv-ic.d work 



of the Expedition. 



