Fbovbssor Thomas Thomson on Coal Gas. 173 



1000 feet of Lesmahagow coal, . . 8s. 



— Skaterig coal, . . . 9s. 4i<L 



— Glasgow coal, . . .lis. Bid. 



— Ditto, south side river, . 13s. 5|d. 



After this paper was read, an interesting discussion took place, 

 during which Mr. John Hart made the following observations : — 



Having heard that Lord Dundonald used gas from coal as a light 

 long before Mr. Murdoch's discovery, and being in Culross Abbey 

 while it was unroofed and in a state of ruin, I naturally began to 

 examine the walls to see if I could discover any trace of the pipes, 

 when Sir Robert Preston's gardener informed me, that he believed no 

 pipes were used, as some of the old people of Culross who saw it, told 

 him that the gas was carried in a vessel from the tar works and burnt 

 in the Abbey. 



I afterwards discovered that an intelligent old man, a blacksmith in 

 our neighbourhood, had been long in the employment of his Lordship, 

 and that he had been his assistant in many of his experiments about 

 that period ; from him I received the following account : — His Lord- 

 ship having been in company with some scientific friends, on the fol- 

 lowing morning he mentioned to his blacksmith that, on the previous 

 night, he had been shown a work * which gave an account of a process 

 for distilling pit coal, and from which a substance like tar might be 

 obtained in considerable quantities. This he wished to try, as he 

 thought it might be made to serve the purposes of common tar ; and 

 he then told him to come along with him to the garden, where he 

 pointed out a spot, and gave him instructions to set about the erection 

 of an oven or kiln to try it : the experiment succeeding, nothing more 

 was done until it was secured by a patent. Soon after, nine cylindrical 

 ovens of brick were built in a row, along a bank of earth ; these were 

 about 3 feet in width and about 7 feet deep, being hemispherical at top 

 and bottom, each having a moveable cover at top for charging, and a 

 well fitted door at bottom to regulate the combustion : a 7 inch cast 

 iron pipe near the top conveyed the products to the condenser on the 

 top of the bank. The condenser was a flat box of lead, having 

 divisions partly crossing it to detain the vapours of the tar, and very 

 much resembled the coolers used by brewers, from having a rim to 

 retain cold water on its upper surface, with which it was plentifully 

 supplied. The tar was conducted by a pipe into similar cylinders of 

 brick-work on the opposite side of the bank; each of these had a 

 small opening in the top for the escape of the incondensible part of 



♦ This might probably be Dr. Richard Watson's Chemical Essays, published in 1787, 

 in which he details experiments he made on the distillation of pit coal, and also the 

 quantities of coke and tar obtained from varioiis kinds of coal. 



