132 
hardness had to do with the strength and elasticity of these 
small specimens of cast iron. For this purpose he plunged 
some of them at a heat near the melting point into water, 
then selecting those which had been hardened sufficiently to 
resist the action of the file. Others he cooled slowly from 
a bright red heat. The experiments were conducted in the 
manner described in the last number of the Proceedings. 
No. of 
Length of 
Breadth of 
Depth of 
Breaking 
Experi- Nail between 
Nail at 
Nail at 
Deflection. 
Weight. 
ment. 
Supports. 
Fracture. 
Fracture. 
Lbs. 
03 
' 1 .... 
.. 10 ... 
...o-ll ... 
... 0-122 ... 
... -0067 .. 
....129 
"cS 
2 .... 
.. 1-04 ... 
... 0-12 ... 
... 0-12 ... 
... -0037 .. 
.... 84 
3 .... 
.. TO ... 
... 0-12 ... 
... 0122 ... 
... -0028 .. 
.... 81 
V 
4 .... 
.. 1-02 ... 
... 0-143 ... 
... 0-102 ... 
... -0077 .. 
....129 
K 
5 .... 
.. U ... 
... 0-138 ... 
... 0-13 ... 
... -0071 .. 
....203 
Average 
1-032... 
... 0-1262... 
... 0-1192... 
.. -0056 .. 
...125.2 
m 
6 .... 
.. 1-0 ... 
... 0-112 ... 
.. 0-117 ... 
... -0088 .. 
....141 
*3 
7 ... 
.. 1-05 ... 
... 0-139 ... 
... 0-114 ... 
... -0087 .. 
....150 
5zj J 
8 ... 
.. 1-02 ... 
... 0-130 ... 
.. 0-138 ... 
... -0051 .. 
....176 
9 ... 
.. 1-04 ... 
... 0-117 ... 
.. 0-090 . 
... -0101 .. 
....101 
m 
10 .. 
.. 1-04 ... 
... 0-121 ... 
.. 0-108 ... 
... -0073 .. 
....113 
Average 
1-03 ... 
... 0-1238... 
... 0-1134... 
... -008 .. 
...136.2 
Reducing to a length of 3 feet and 1 inch square section, 
and making a deduction of \ from the deflections, on account 
of the taper of the nails, the above results, along with those 
in the last number of Proceedings, become 
Breaking W eight. Deflection. 
Nails in original state 2673 ’922 
Hardened ditto 2002 -677 
Softened ditto 2448 -924 
Dr. Joule exhibited three photographs of the sun taken 
on the 1st December, 1858. The images, '43 in. diameter, 
were produced by the achromatic object-glass of a telescope 
with half-inch stop. Exposure, by means of an apparatus 
completely detached from the camera, during a small frac- 
tion of a second. He had been induced to examine them 
after seeing the beautiful photograph of the late eclipse by 
Mr. Brothers. On examining the three images a nebulosity 
