28 PROFESSOR C. V. BOYS ON THE 
plunger was forced down upon its shoulder. The solid metal was thus under great 
pressure made to flow, and a quantity of wire was forced out of the small side hole. 
Under these circumstances cavities are impossible, and since pure metal was employed, 
variations of density were out of the question. It may be worth mentioning here 
that of all metals in commerce, lead may be obtained of a greater degree of purity 
than any other. As soon as the pressing had been completed, the mould was 
removed, and allowed to cool. On being opened the lead ball was found perfect in 
form, and, so far as it is possible to judge, perfect in every respect, or at any rate so 
perfect that any departure from such a state cannot produce a disturbance in its 
gravitative power which is comparable with the limits of accuracy with which the 
attractions can be observed. I have made four balls of the 44-inch size, numbered 1, 
2, 3, and 4, but I have at present used only numbers 1 and 2. Besides these I have 
made four of the smaller size of 24 inches in a mould of the same construction and 
numbered them numbers 6, 7, 8, and 9. To avoid risk of injury, the balls are kept 
in pairs in four well-made mahogany boxes, with two velvet-lined hemispherical 
hollows, in each half of each of the boxes. I have made lifters also to raise them by 
their brass lugs. 
I weighed these balls on August 18, 1891, on the large Oertling balance in the 
South Kensington Museum. Through the kindness of Mr. Coanry I was able to 
find the true value of all the weights employed, by comparison with the standards 
at the Standards Office. The weights of the two lead balls made use of, with their 
included brass ball-holders are, taking due account of the corrections :— 
NOME eRe. eee LO oman. 
Qe Nae ear Gait oie ela Om LG tears 
37 
The lead balls are suspended from the geometrical clamps at the tops of the lid 
pillars by phosphor-bronze wires, which I drew myself down to the smallest size that 
I considered safe. This was found by measure to be ‘0232 inch in diameter. As it 
had to carry 16°33 lbs., the stress would be one of between 15 and 16 tons to the 
square inch only, or about one-third of what I had found the wire able to carry. I 
could not silver-solder the wire into the upper and lower connecting pieces, as the 
strength was destroyed by annealing, and I found that soft solder allowed it slowly 
to creep out even when it was soldered into a hole which it nicely fitted, and 4 inch 
long. I overcame this minor difficulty by dipping the ends of the wires into copper 
solution and thickening them by electro-depositing copper until they were just too 
large to enter the enlarged holes prepared for them. I then drew them through holes 
in a draw plate down to the right size. They were then sweated into their places, 
and the end of the wire at the upper end bent over at the bottom of the slot where it. 
just protruded, hammered down and again sweated ; while at the lower end a small 
transverse hole was drilled on each side so as just to touch the side of the wire, and 
pins driven in, and the whole sweated together. This was done on September 2nd, 
