TRANSACTIONS OF SECTION A, 415 
or burnt out by his concentrated beams; and inasmuch as the sun continually 
changes his position, not only from hour to hour, but from day to day, it follows 
that different portions of the wood will be acted upon, not only from one hour to 
another, but also from one day to another.’ 
The blocks are all of mahogany, being, as nearly as possible, of the same 
quality ; and the diameter of the sphere is about 52 inches. 
All the blocks have been treated by us in the same way. The hollows burnt 
out have been filled with a mixture of bees’ wax and olive oil of such a consistency 
that we could easily work it into the burnt cavities until the whole internal 
hemisphere should be made to present the same smooth surface which it had before 
it was burnt. A comparison of the weight of the (previously saturated) block 
before and after the process was supposed to give us a good estimation of the 
extent of the hollows. The mean of two such determinations was taken, and the 
near concordance of the two will show that the results are as accurate as the nature 
of the experiment requires. 
As the wax used for the second series was not necessarily the same as that used 
for the first, we caused six bowls of the first series to be refilled with the second 
series wax and weighed, by which means we obtained the coefficient necessary to 
reduce the second series to the same standard as the first. 
There still, however, remains the fact that the first series were made at the 
Board of Health (now the Local Government Board), at Richmond Terrace, 
Whitehall, while the second were made at the Kew Observatory. 
The last bowl treated in the old series was that ending December 1874, and the 
first of the new series, that ending June 1875, is defective, owing to the shadow of a 
‘post falling on it. We have, therefore, rejected it from our list. Mr. Shaw, 
student at Owens College, was good enough to assist us in the determinations of the 
Kew set. The specific gravity of the mixture of wax and oil used for this set was, 
at 74° C., 0:838, and the melting point was 61:5° C. 
In the following table we have the results obtained :— 
Taste I.—Weicut or MIxtTuRE FILLING THE Hottows or tHE Kew Bowtis. 
: First Second 
Date Experiment | Experiment Mean 
I. | June 24, 1875, to Dec. 22,1875. . 24-4 24-4 24-4 
II. | Dec. 21, 1875, to June 23,1876. . 33°0 33°8 33°4 
IIl.* | June 22, 1876, to Feb. 2,1877. . 39-0 39-2 3971 
IV.*| Feb. .2,1877,to June 21, 1877... 16°6 16:2 16°4 
V. | June 21, 1877, to Dec. 21,1877. . 26°8 27:8 27:3 
VI. | Dec. 21, 1877, to June 21,1878. . 19-9 19°8 19°8 
VII. | June 21, 1878, to Dec. 21,1878. . 25°6 26-2 25°9 
VIII. | Dec. 21, 1878, to June 21,1879. . 22°4 22:1 22°3 
IX. | June 21, 1879, to Dec. 21,1879. . 18°6 18:2 18-4 
X. | Dec. 21, 1879, to June 21,1880. . 21:2 20°5 20°8 
XI. | June 21, 1880, to Dec. 21,1880. . 13°3 12:9 13-1 
XII. | Dec. 21, 1880, to June 21,1881. . 13°3 13°6 13:5 
XIII. | June 21, 1881, to Dec. 21,1881. . 35°3 355 ODES 
XIV. | Dec. 21, 1881, to June 21,1882. . 24:1 24°2 24-2 
XV. | June 21, 1882, to Dec. 21, 1882. 28°8 28:2 28-5 
It will be seen from this table that the change of bowls was always made as 
nearly as possible at the solstice, with the exception of two occasions—viz. No. 
IiI., where the bowl was inadvertently allowed to remain from June 22, 1876, to 
February 2, 1877, and No. IV., where the observation was made from February 2, 
1877, to the ensuing solstice. Thus No. III. embraces a larger and No. IV. a 
smaller interval than usual. 
We are afraid that No. III. must be rejected, as the image of the sun must 
have travelled twice over part of the wood, and we do not know how to correct for 
this, With regard to No. IV., it will perhaps be sufficient to increase it propor- 
