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VIII. — Observations of the Edinburgh Rock Thermometers. By Thomas Heath, B.A. , 

 Assistant Astronomer, Royal Observatory, Edinburgh. (With Four Plates.) 



(Read February 18, 1901.) 



The New Rock Thermometers. 



The accompanying Tables I. and II. contain the readings from May 1888 to December 

 1899 of the new set of deep rock thermometers erected in June 1879 at the Calton 

 Hill Observatory, to replace the old set which were destroyed in September 1876. The 

 tables are in continuation of, and are similarly arranged to, those published by the 

 Royal Society of Edinburgh in Vol. XXXV. part 3 of the Transactions, along with 

 a paper by the late Prof. Piazzi Smyth. The tables published with Prof. Smyth's 

 paper contain the observations made between October 1879 and April 1888, being the 

 beginning of the series with the new set of thermometers. 



The construction, testing, and placing in position of these thermometers have already 

 been described at length in a previous paper by Prof. Smyth, published in Vol. XXIX. 

 part 2 of the Transactions. It is unnecessary therefore to do more than recapitulate 

 here the principal facts concerned in the mounting of the instruments. The contract 

 for the construction of the thermometers was given to Messrs Adie & Sons, Opticians, 

 Edinburgh, and the actual work was carried out by their foreman, the late Mr Thomas 

 Wedderburn, under the immediate superintendence of Mr R. Adie. The thermometers, 

 when originally placed in the bore-hole in the rock of the Calton Hill, were arranged as 

 follows, counting from the surface of the rock to the centres of their respective bulbs : — 



t v at a 



depth 



of 250 inches. 



^2' " 



M 



125 „ 



^3' >> 



»J 



50 „ 



^4> ); 



?? 



25 „ 



There was also a similarly constructed thermometer placed with its bulb an inch under- 

 ground, and an air thermometer was hung inside the box with its bulb a few inches 

 above the surface. All, except the air thermometer, had 30 inches of tube, of wider 

 calibre than the rest of the stem, attached to their upper ends above the surface, for 

 scale readings. In their construction care was taken to make the tubes and bulbs in 

 all particulars similar to the old thermometers, broken pieces of which had been retained 

 for patterns. The stems are, however, shorter than the old ones. After each thermometer 

 had been put in place, fine sand was poured into the hole in sufficient quantity to receive 

 the next shorter thermometer, till the whole set was in place. In the case of the old 

 set the mouth of the hole was closed with plaster of Paris, or some such material. This 

 VOL. XL. PART I. (NO. 8). Z 



