xlii EIGHTH REPORT — 1838. 



Medical Section, including several subjects of physiological interest 

 reported upon in the present volume, are remarkable for that spirit of 

 co-operative labour which has not been common in this country, and 

 which it is one of the liappiest effects of these meetings to facilitate 

 and encourage. In like manner, a question of great interest as re- 

 gards one of the most important products of our mineral wealth and 

 national industry, which had been discussed with more than common 

 warmth and earnestness at former meetings of the Association, has 

 been examined by an analysis, performed by one of the most distin- 

 guished chemists of the present day, of the iron produced by the ap- 

 plication of the hot and cold blast respectively ; which was undertaken 

 at the request of the Chemical Committee, combined likewise with 

 experiments, on an extensive scale, upon its relative strength and other 

 properties, which were commenced at the desire of the Mechanical 

 Section, by Messrs. Hodgkinson and Fairbairn, whose profound and 

 extensive knowledge of practical mechanics so well qualified them for 

 a task which they have executed with singular ability, enterprise, and 

 skill. The experiments on Waves, which are detailed in Mr. Russell's 

 report in our present volume, were likewise undertaken at the request, 

 and carried on by the aid of the funds of the Association. The accu- 

 rate conception of a wave, its origin, propagation, and laws, is one of 

 the most difficult and fundamental of those which are required in 

 many of the delicate and embarassing inquiries of natural philosophy ; 

 and the experiments of Mr. Russell are well calculated to illustrate 

 and confirm many of the results which the mathematician has deduced 

 from the theory of fluid motion. Adhering, therefore, to our design 

 of mainly noticing those parts of our recent transactions winch illus- 

 trate the prominent points in our system of operations, we shall con- 

 clude our remarks by noticing a report by Prof. Johnston, on a new 

 and curious subject of chemical inquirj^, as aflfbi'ding a good example 

 of the execution of an object which the Association has had much in 

 view. The discovery that there exist definite chemical substances, 

 which are capable, under certain conditions, of assuming more than 

 one crystalline form, not deducible from nor referable to each other, 

 and accompanied with different physical properties ; and furthermore, 

 that there are instances of substances which are capable (independently 

 of any change of composition) of undergoing some internal transmu- 

 tation sufl[icient to vary even their chemical aflinities : these are dis- 

 coveries which, pointing out a new road to the investigation of the 

 hidden mysteries of molecular attractions, peculiarly deserve to be 

 verified and extended. But it so happens that they have been little 

 studied or prosecuted in our country ; and, therefore, the Chemical 

 Committee, in accordance with one of the prominent designs of the 

 Association, selected this particular point as the subject of the Report 



