226 Sir Thomas Brisbane's Observations on the 



temperature 50°. One of the pieces of metal is then to be in- 

 troduced (lead for instance ;) the cover D, with its tube and 

 scale, is now to be screwed on, and the water that remains in 

 the tube A is to be made to stand at the beginning of the 

 scale, by screwing the small screw C into it The tube A and 

 its contents being at temperature 50°, the apparatus is then 

 ready for an experiment. The tube A and its contents is then 

 to be heated to 100°, by immersing it in water at that temper- 

 ature. The lead will now expand and force the water up the 

 tube E, for example, to twelve inches. The lead is now to be 

 removed, and the next piece to be introduced, (tin.) All things 

 being in the same state as at the commencement of the former 

 experiment, the apparatus is again to be heated to 100° ; the tin 

 and water will now expand to six inches. From this we may in- 

 fer, that lead is twice as expansible as tin. The same opera- 

 tion is to be repeated with each of the other metals or solid 

 bodies under trial. 



By knowing, also, the contents of each inch of the bore of 

 the tube E, by deducting from the expansion of both the wa- 

 ter and metal, that of the water alone, which must be previous- 

 ly ascertained, we may be able to tell the total expansion of 

 each of the substances in parts of cubic inches. 



Art. VIII. — Observations on the Mean Temperature of the 

 Earth at Sydney > made in the year 1824 and 1825. Com- 

 municated to the Editor by Sir Thomas Makdougall 

 Brisbane, K. C. B. F. R. S. London and Edinburgh. 



Among the numerous and important scientific inquiries insti- 

 tuted by Sir Thomas Brisbane in New South Wales, those 

 relative to the mean temperature of the earth hold an impor- 

 tant place. The following annual series of observations on 

 the temperature of deep wells, is doubtless the most complete 

 that has ever been made, and affords interesting data for va- 

 rious scientific speculations. 



The mean temperature of the earth at Sydney, as obtained 

 from the last column, is 63°.8, differing only the fraction of 



