86 BEPORT— 1882. 



pebble beds of the Bunter or Lower Trias, and the boring was executed at 

 the rate of nearly 100 feet per month. 



The boring at Swinderby, near Scaele (Lincoln), in search of coal 

 (VIII., IX.), was carried to a depth of 2,000 feet, with a diameter at the 

 lower part of only 3^ inches — a circumstance favourable to accuracy, both 

 as impeding convection and as promoting the rapid escape of the heat of 

 boring. The temperature at the bottom was 79°, the water having been 

 undisturbed for a month, and this by comparison with an assumed surface 

 temperature of 50° gives a rate of 1° in 69 feet. 



The rocks are Lower Lias, New Red Marl (569 feet thick), New Eed 

 Sandstone (790 feet thick). Red Marl, and earthy Limestone. 



The following results have been obtained from shallow borings. The 

 first three were made under Sir William Thomson's direction, with a 

 thermometer which could be read by estimation to hundredths of a 

 degree : — 



Bltthswood bore, near Glasgow (I.), with a depth of 347 feet, gave a 

 very regular increase of 1° in 50 feet. 



KiRKLAND Neuk bore, in the immediate vicinity of the above (II.), 

 gave consistent observations at difPerent seasons of the year from 180 feet 

 to the bottom (354 feet), the rate being 1° in 53 feet. This bore passed 

 through coal which had been ' very much burned or charred.' 



South Balgeat bore, near Glasgow, and north of the Clyde, with an 

 available depth of 625 feet, gave, by comparing the temperature at the 

 bottom with that at 60 feet, a rate of 1° in 41 feet. 



Shale extends continuously from 390 to 450 feet from the surface, and 

 the increase in these 60 feet of shale was 2°-02, which is at the rate of 

 1° in 30 feet. This rapid increase agrees with the fact that shale has 

 very low conductivity, averaging -0019 in Professor Herschel's experi- 

 ments. 



The only small bore remaining to be mentioned is that at Manegaon, 

 in India (X. 198), which had 310 feet available, and gave by comparing 

 the temperature at this depth with that at 60 feet a rate of 1° in 68 feet. 

 The rocks consist of fine softish sandstones and hard siltv clays, the dip 

 being 10°. J J ' f 



The following results, obtained from observations at the bottom of 

 shafts with only a small depth of water, are not altogether without value, 

 ^ihough the circumstances are not favourable to accuracy : — 



Two shafts of salt mines near Cakrickfergus (Ireland) (II. 12, 13), 

 with depths of 570 feet and 770 feet, gave by comparison with an assumed 

 surface temperature of 48° rates of 1° in 40 feet and 1° in 43 feet. The 

 sod in both cases was yellow clay, a substance for which Professor 

 Herschel finds the low conductivity of "0025. 



In a ' sump ' at the bottom of Slitt mine, in the Allenheads lead 

 mines, Weardale (Northumberland) (IV.), at 660 feet from the surface, 

 the temperature 65°-0 was found, which, by comparison with the surface 

 temperature, 45°-3, assumed by the observer (Mr. Burns, of H.M. Geo- 

 logical Survey), being a degree higher than the observed air temperature 

 in the neighbourhood, gives a rate of 1° in 34 feet. The strata consist 

 of alternate beds of sandstone and shale, with a few beds of limestone, 

 158 feet of basalt, and 55 feet of fluor spar. 



4. Tunnels.— The Mont Cenis tunnel (IV. 15), which is about 7 miles 

 long, is at a depth of exactly a mile (5,280 feet) beneath the crest of Mont 

 Frejus overhead. This was the warmest part of the tunnel, and had a 



