COMPLETION OF THE NEW ROCK THERMOMETERS. 647 
No; TE 
Supplied by R. Apiz, Esq. 
The Earth Thermometers in the Observatory Grounds, Calton Hill. 
In the XIth volume of the Astronomical Observations made at the Royal Observatory 
1849-54, there is, pp. 225-279, an account of the earth thermometers, with observations from 
1837-54. This paper contains all the information in detail in regard to structure, and correc- 
tion for surface temperatures on the stems of the long tubes. What is there stated applies 
to the thermometers inserted by us on 18th June 1879, in the bore of the rock occupied by 
the first set. 
An accident destroyed the thermometers of 1837; to replace them it was necessary to 
clear the broken stems of the old tubes out of the bore. In doing so, we found the clay placed 
on the surface to have changed, through 42 years’ exposure to rain, into a piece of hard rock, 
which held the glass tubes of the thermometer stems very firmly. After removing the stone 
containing the stems of the tubes, the sand and clay for a depth of six inches was partially 
indurated, when we reached the sand in the state that it had been inserted. 
When the bore had been cleared of the old sand, we found that when empty it acted as 
a perpendicular drain, receiving water from the fissures in the rock which quickly passed away 
with dry weather. 
In the new set of the thermometers, clay on the top of the sand has not been used, as we 
consider it unsafe to bind the tubes therewith; one of the 1837 set having been broken in a 
frosty morning when so bound. The scales of the new set of thermometers are platina, and 
fastened to their respective tubes with platina wire. 
(Signed) Aex. Avie & Son, 37 Hanover Street, 
Sth January 1580. 
No. III. 
Account of the Making and Placing of the New (1877-79) Rock Thermometers at the Royal 
Observatory, Edinburgh, by THoMAS WEDDERBURN, Foreman of the Firm of Apiz & Sons, 
Opticians, Edinburgh. 
On our receiving the order from Professor Prazzi Smytu for the reconstruction of the 
destroyed earth or rock thermometers, it was considered that, in the first place, the hole that 
they were sunk in should be cleared out, and on our clearing off the surface mould we found a 
hard compact substance instead of a “puddle clay” as mentioned in the Observatory Transac- 
tions. The sections of the tubes now being seen, we then found the substance to be about 6 
inches thick in the hard state, and then gradually softening for other 3 inches until it came in 
contact with the sand that filled the hole. As it was wanted to be ascertained if the portions 
of the thermometers underground were the same in construction as what the new thermometers 
were to be, we proceeded to remove the hard mass, with the sections of the tubes, and then the 
sand, until we got down to the 3 feet thermometer bulb, which we removed; then to the 6 feet 
bulb, which was also removed; but on reaching down to the 12 feet bulb it was found to be 
firmly fastened to the side of the hole by the rust of its tin case, so that we had to give up 
hopes of bringing it to the surface. We then proceeded in a rough and ready way, by means 
of a 30 feet pole with 3 feet of 2 inch brass tube attached to it, to remove the rest of the 
contents of the hole, which was found to be 264 feet deep, the opening at surface, 53 to 5 inches: 
