KX REPORT—1846. 
Among the many useful national objects which have been promoted by 
the physical researches of the British Association, there is one which calls 
for marked notice at this time, in the proposal of Mr. Robert Stephenson to 
carry an iron tube or suspended tunnel over the Menai Straits to sustain 
the great railway to Holyhead. This bold proposal could never have been 
realized, if that great engineer had not been acquainted with the progress 
recently made in the knowledge of the strength of materials, and specially of 
iron ; such knowledge being chiefly due to investigaticns in which the Asso- 
ciation has taken and is still taking a conspicuous share, by the devotion of 
its friends and the employment of its influence—investigations which have, 
as you know, been prosecuted with great zeal and success by its valued mem- 
bers Mr. Hodgkinson and Mr. Fairbairn. I may further state, that in the 
recent improvements in railways the aid of scientific investigations having 
been called for by the civil engineer, to assist him in determining with accu- 
racy the power to be provided for attaining the high velocities of fifty and 
sixty miles an hour; it was found and admitted by the most eminent en- 
gineers, that the very best data for this purpose, and indeed the only experi- 
ments of any practical value, were those which had been provided for some 
years ago by a Committee of the British Association, as published in our 
Transactions. Let such results as these be our answer when we are asked, 
what have been the useful objects attained by the British Association! 
However imperfect my knowledge of experimental philosophy may be, I 
must now notice that the last volume of our Reports contains two contribu- 
tions to it, in which subjects of the deepest theoretical and practical interest. 
have been elucidated, at the request of the Association, by the labours of 
our foreign coadjutors. 
That some substance of a peculiar kind everywhere exists, or is formed in 
the atmosphere by electrical agency, both natural and artificial, had long been 
suspected, especially from the persistency of the odour developed by such 
agency, and its transference by contact to other matter. Professor Schon- 
bein, to whom I shall hereafter advert as the author of an important practical 
discovery, is, however, the first philosopher who undertook to investigate the 
nature of that substance; and though the investigation is not yet complete, 
he has been enabled to report no inconsiderable progress in this difficult and 
refined subject of research. 
A request from the Association to Professor Bunsen of Marburg, and our 
countryman Dr. Lyon Playfair, coupled with a contribution of small amount 
towards the expenses involved in the undertaking, has produced a report on 
the conditions and products of iron-furnaces which is of considerable value in 
a commercial view to one of the most important of our manufactures, and 
possesses at the same time a very high interest to chemical science in some 
of the views which it developes. On the one hand it exhibits an entirely 
new theory of the reduction, by cyanogen gas as the chief agent, of iron 
from the ore; on the other it shows, that in addition to a vast saving of fuel, 
about 2 ewt. of sal-ammoniac may daily be collected at the single establish- 
ment of Alfreton, where the experiments were made; thus leading us to 
infer that in the iron-furnaces of Britain there may be cbtained from vapour 
which now passes away, an enormous quantity of this valuable substance, 
which would materially lessen the dependence of our agriculturists on foreign 
guano. It is, indeed, most gratifying to observe, that in pursuing this inquiry 
into the gaseous contents of a blazing furnace of great height, our associates 
traced out, foot by foot, the most recondite chemical processes, and described 
the fiery products with the same accuracy as if their researches had been made 
on the table of a laboratory. Weighed however only in the scales of absolute 
