84 Mr. George Thomson <m Blast Fu/maces. 



exogenous plants the granule is more complicated, has two, three, 

 or four enveloping membranes, assumes various forms, such as 

 threo-lobed, spherical, or triangular, and emits pollen-tubes varjing 

 from three to upwards of fifty. Natural orders are characterised by 

 having a pollen granule of one type, and the more natural an order 

 the more frequently will this be the case. 



J. H. B. 



4:th Januaryy 1843, — The President in the Chair. 



Messrs. Peter M'Intosh, George Sutherland, and Thomas Hill, were 

 admitted as Members of the Society. The following communication 

 was read: — 



XXIV. — Practical BemarTcs on Blast Furnaces. By George 

 Thomson, Esq., Mining Engineer. 



There is a manifest absence of any thing like correct principle in 

 iron smelting ; and although the reduction of ore by cementation may 

 be an easily explained operation, yet, the peculiar combinations brought 

 to bear in the blast furnace, seem to present a problem which chemical 

 science is as yet unable to explain. 



In the attempted solutions of the problem, a too limited number of 

 facts have been generally considered, and generalizations attempted, 

 from facts bearing partially on unvaried conditions. Following the 

 system of induction, if a true principle is only to be attained through 

 the medium of facts in every variety and under every possible condition, 

 the object may be assisted, in some measure, by my laying before the 

 Society a few facts which have come under my own observation, and 

 may be peculiar. The results given are divided into three principal 

 conditions, viz: 1st, as respects the direct influence, coeteris paribus^ 

 of different material. 2d, Influence of shape and size. 3d, Influence 

 of blast, as to diffusion, pressure, or quantity. 



1st, Influence of material. — Although all the materials used in 

 smelting have a certain influence ; it is the coal which gives the most 

 extraordinary results as respects " yield." A few results of various 

 coals are therefore collected into the following table from my own 

 immediate observation. The word "yield" is used to denote the 

 comparative quantity of coals used in the furnace, to produce, or to 

 smelt a ton of iron. In the table, the weekly quantity of iron given, 

 as produced by hot blast, is small in comparison with what is now 

 made at most furnaces ; yet these are the more correct comparative 

 results, having been attained with like conditions of size, shape, number 

 of tweres, &c. Since that time, the shape and size of furnaces have 

 been materially altered, as well as other conditions, and the make 

 greatly increased. 



