686 PHILOSOPHICAL TRANSACTIONS. ' [anNO 1775. 



for 10 years ; but as these observations were made at 8 o'clock, in the morning 

 and 4 in the afternoon, and yours at 8 o'clock, in the morning and 2 in the 

 afternoon, the corresponding years of the morning's observations only admit of 

 a comparison. It appears by your register, that the mean heat at London for Q 

 years, from the end of 17-63 to the end of 1772, at 8 o'clock in the morning, 

 was 47''.4 ; and the mean heat at Hawkhill, during the same period of time, 

 was 46". The difference of which is only 1°.4. A difference much less than 

 might be expected from the difference of latitude, and not sufficient to account 

 why nonpareils, golden rennets, peaches, nectarines, and many kinds of grapes, 

 generally come to maturity near London, and scarcely ever near Edinburgh, 

 without the aid of artificial heat. Before proceeding further to perplex myself 

 with this difficulty, I procured from Hawkhill and from yourself the register of 

 the thermometer for 3 years, at the same periods of time. And by these it 

 appears, that the mean heat of London of these 3 years exceeded that of Edin- 

 burgh, by 4^5. And the mean heat of the 3 hottest months in London 

 exceeded the mean heat of the same 3 at Edinburgh, by 5°.8. And the mean 

 heat of these 3 summer months, at 2 o'clock in the afternoon in London, 

 exceeded the mean heat of the same months, at the same hour, in Edinburgh, 

 by 7°-3 ; which sufficiently accounts why some fruit may come to maturity in 

 one country and not in the other : and also why corn and grass, which vegetate 



for the manufacture of certain useful preparations in chemistry. Extending his practice and projects 

 in this line, he next established a manufactory of oil of vitriol at Prestonpans, in Scotland, in the 

 year 1749 ; after which he made that country his chief residence. Dr. R.'s chemical practice 

 leading him to experiments on smelting iron stone, and preparing that metal, which he did by 

 means of pitcoal, he was thus gradually induced to establisli, at Carron, the greatest manufactory 

 of iron in this country. Thus, by the force of his own genius and great exertions, he established 

 three very large and profitable manufactories, the laboratory at Birmingham, tha oil of vitriol works 

 at Prestonpans, and the iron works at Carron, all which are still carried on with great emolument to 

 the several proprietors. Unfortunately however for Dr. R. he was induced successively to relinquish 

 each of these concerns, to employ his capital on the next in succession, and finally to tliat of a large 

 concern in coal-mines, in which his whole fortune was sunk and lost ; to the grievous embitterment 

 of the latter years of his life. 



From a man so deeply and so constantly engaged in the detail of active business, many literary 

 compositions were not to be expected. It has been happily said tliat Dr. R. left behind him many 

 works, but few writings. The great object he kept constantly in view, was to promote arts and 

 manufactures, rather than to establish theories or hypotheses. The above paper, on the comparison 

 of the heat of London and Edinburgh ; with anotlier, in these Transactions, of experiments on 

 ignited bodies ; and one in the Edinburgh Transactions, on the filling and ripening of corn, are all 

 his essays that have been published, besides two political pamphlets. The paper on ignited bodies 

 was occasioned by a report of some experiments made by the celebrated Buftbn, from which he had 

 inferred tliat matter is heavier when hot than when cold. But Dr. R.'s experiments, made with 

 great accuracy before a committee of the r. s. at London, seem to refute that notion.— See a pretty 

 large and circumstantial account of Dr. R.'s concerns in the Supplement to the Encyclopaedia 

 Britannica, from which thp above particulars are extracted. 



