130: Further Experiments on the [Marcw, 
Taiz IV.—Dew point (S), calculated from the Depression in Table II. 
Comparative Tension (T), and Grains of Aqueous Vapour in a cubic 
JSoot of Air (G.) 
Year and S. T. | G. Year and Ss. | T. G. 
Month. Month. 
; 0 0 
Dec. 1830, ..| 31,8 ,338 | 2,37.[Dec. 1831, ..}| 48,6 683 4,26 
Jan. 1831, 34,0 370 | 2,57 JJan. 1832, ..| 36,9 445 2,84 
February, 41,6 3028 | 3,33 [February, .. 36,5 418 2,80 
March,...... 45,5 ,372 ; 3,74 |March, 35,5 »299 2,66 
Aprile. ater. ie 46,2 3200 Fe Se7 Aprile cons. 38,6 | 196 2,84 
May,. ...... 48,9 | ,224 | 4,03 |May, ...... 40,4 ,201 | 3,00 
June, ...... 67,9 5463, ||) 7DORUNE Tar) 6 61,9 379 6,20 
July, 71,6 606 | 8,56 Duly, ...... | 71,4 617 8,52 
August, 74,4 ,759 | 9,45 JAugust, .... 72,0 738 8,77 
September, ..| 70,0 | ,685 | 8,21 |September, .. | 62,4 | 5533 | 6,43 
October, .... 55,4 »449 | 5,17 |October, ....| 35,6 215 | 2,62 
November, .. | 43,0 438 | 3,47 |November, .. | 40,2 3336 3,07 
Means,...... 52,5 458 | 5,02 |Means, 48,3 422 | 4,50 
a a ED 
III.—Determination of the Constant of Expansion of the standard 10-feet 
Iron Bar of the great Trigonometrical Survey of India ; and expansions 
of Gold, Silver and Copper by the same Apparatus. By Jas. Prinsep, 
F.R.S. Sec. 
When I submitted the results of my former experiments on the exe 
pansion of iron, brass, and lead, which were printed in the Gtranines 
1n Scrence for December, 1831, I ventured to anticipate that the simpli- 
city of the process then contrived for heating the metals would be a re- 
commendation for its adoption in any future researches of a similar na- 
ture. The opportunity has not been long wanting ; and as it has involved 
the necessity of a more scrupulous degree of accuracy, from the import- 
ant purpose to which the results were to be applied, I feel it incum- 
bent upon me to enter into fuller detail in describing the course of 
experiment pursued. The gigantic scale of the former trials, with bars 
of twenty-five feet in length, was calculated to obviate most of the 
errors of observation, as well as any want of extreme delicacy in the 
measuring apparatus; but on the present occasion, although the bars 
were of smaller dimensions, the other concomitants were much more 
ratisfactory; and I may confidently maintain that, with the present and 
the former series, we now possess amore correct table of the dilatations 
of gold, silver, iron, copper, brass, and lead, than have been hitherto 
published in works of natural philosophy. | 
