180 



Depth. 



ft. 



360 



390 



420 



450 



480 



525 



KEPORT 1869. 



July 1869. South. Balgray Bore {continued). 



Nature of strata. 



Number 

 oflayers. 



Dark fakes .... 

 Fakey sandstone 

 Dark blaes .... 

 Ironstone .... 



Dark fakes 

 Dark blaes 

 Sandstone 



Dark blaes 



Dark blaes .... 



Dark blaes .... 

 Dark limestone . 

 Light do. hard 

 Limey fakes 

 Parting .... 

 Fakey limestone 



Fakey limestone 

 Greenstone . . . 



Thickness. 



Tempera- 

 ture. 



3 



2 



20 



3 

 1 

 3 



1 

 4 

 4 

 1 

 1 



11 



ft. in. 



11 4i 



25 7 



17 6i 



5 6 



60 



19 8J 

 6 U 

 3 ll' 



30 



30 



30 



6 41 

 3 1 



7 

 13 1 



1 



41 



30 



10 

 34 



lOi 

 U 



45 



53-88 



55-40 



56-11 

 57-14 



58-13 



58-70 



59-52 



Diflter- 



enoe. 



1-52 



0-71 



1-03 

 0-99 



o-s: 



0-82 



Difference 



23er foot. 



0-0253 



0-023/ 



0-0343 



^ 9 



0-0330 





0-0190 



0-0182 



Diiference of temperature for 465 feet . ll°-32, 

 Mean difference of temperature per foot 0°-0244, 



being at the rate of 1° for 41 feet. It will be remarked that the shale, 

 ■which extends from 390 feet to 450 feet, shows a more rapid increase of 

 temperature, and therefore smaller conductivity than the other strata*. 



The following is an account of the strata penetrated by the Blythswood 

 bore (No. 1), together with an abstract of the temperatures observed in it. 

 The particulars of the observations of temperature were given in last year's 

 Report. 



* As regards the relation between rate of increase of temperature do-wnwards and 

 thermal conductivity, it is to be borne in mind that in comparing different parts of one 

 bore these quantities ai-e generally in inverse proportion to each other ; but this rule does 

 not apply to the comparison of two bores in different localities. See Mr. Hopkins's paper, 

 Phil. Trans, vol. cxlvii. 



