648 PROFESSOR PIAZZI SMYTH ON THE 
in diameter; the first 12 feet of it was much the same, after which it closes to a hole of about 
3 inches diameter for the remainder of the depth. We may state here that we found some 
obstruction in removing the sand from a copper wire about the 20th of an inch in diameter. 
There having been no evidence of it when opening out the hole, we could only bring it up 
in small portions. On showing these to Professor ALEx. 8. HerscHEeL of Newcastle-on-Tyne, 
he thought them to have been portions of a thermal pile (though no written note of such a 
thing has been found), and from the length of wire brought up it must have reached the 
bottom of the hole. 
In proceeding with the construction of the new thermometers, we had carefully retained 
portions of each tube for the size of bore, and having applied to Mr Forp, of the South Back 
of Canongate, for these extra long tubes, we had them drawn on the 14th of August 1877. 
The first five tubes of 40 feet did not come up to what was expected of them, though for the 
shorter thermometers there were pieces of them that answered. It was then proposed to draw 
tubes of a 100 feet, instead of carrying on the drawing of the 40 feet lengths. Ona 100 feet 
tube being drawn, it was found on careful examination to answer the purpose, 30 feet of it 
being cut from the centre. For the scale tubes we had eighteen drawn of 3 feet each, and after 
carefully callipering them, we found them sufficient to answer the purpose. After the tubes 
were drawn they were laid in their “ gutters,” which were made of 26-inch deals, set at right 
angles, with pieces of cork 3 feet apart for the tubes to rest on, where they remained until 
their insertion in the Royal Observatory grounds. In the drawing of the bulbs of the 
thermometers, we had carefully prepared sketches of each size, so that there was no trouble 
in working them, and we may mention that they were annealed, the glass of them being as near 
as possible the 20th of an inch in thickness. 
In the making of the thermometers our first care was to find if we had got the bulbs of 
the right size, which we did by fixing a piece of the scale tube to each bulb, and then filling 
them with spirit, and testing them in the usual way with the standard, when they were all 
found to be correct for each range of bulb. We then attached each bulb to its own tube, and 
in the shorter thermometers filled them with the spirit in the usual way. With the 12 and 
24 feet tubes we turned the bulb ends uppermost, and poured the spirit in through a small 
filler made of inch glass tube drawn to a fine point, until the bulb was nearly filled. The 
points of the bulbs were then sealed, and the thermometer reversed, and a small portion of 
spirit placed in the expansion bulb at top. Then warm water was applied to the bulb to 
expand the spirit and expel the remaining air; the air passing through the spirit in the 
expansion bulb, and allowing it to descend; when after a few applications of heat and 
cold, we had the satisfaction of seeing them filled. 
Our next care was to regulate them, which was done in a tub of cold water, with the three 
standard thermometers made for the purpose, and having fixed the points as near as possible, we 
then had temporary scales of boxwood made and attached to each. They were then removed to 
Professor P1azzi Smytu’s house, at 15 Royal Terrace, for comparison with the three standards, 
In the work of comparing the thermometers, the bulbs were placed in a tub of water, so that 
they were always covered; the temperature of the water being carefully noted, as well as of 
the atmosphere, each time a reading was taken with the three standards, The readings through 
the winter of 1877 and 1878 were but few, from the mildness of the season and the thermo- 
meters being inside the house. Wherefore, to make more certain of the following winter season, 
the thermometers were removed to the outside of the house, where the final readings were got 
in the spring of 1879. 
The three standard thermometers with which the comparisons of the long thermometers 
