Sept. 12, 1889] 



NATURE 



473 



Section A should not be mistaken as the President of Section B. 

 Photogravure and the kindred processes were also inviting 

 subjects on which to dwell, more especially as at least one of 

 them is based on the use of the same material as that on which 

 the first camera picture was taken by Niepce. Again, a dread 

 of trenching on the domains of art restrains me. 



Indeed, it would have been almost impossible, and certainly 

 impolitic, in the time which an address should occupy, to have 

 entered into the many branches of science and art which photo- 

 graphy covers. I have tried to confine myself to some few 

 advances that have been made in its theory and practice. 



The discovery of the action of light on silver salts is one of 

 the marvels of this century, and it is difficult to overrate the 

 bearing it has had on the progress of science, more especially 

 physical science. The discovery of telegraphy took place in 

 the present reign, and two years later photography was prac- 

 tically introduced ; and no two discoveries have had a more 

 marked influence on mankind. Telegraphy, however, has had an 

 advantage over photography in the scientific progress that it has 

 made, in that electrical currents are subject to exact measure- 

 ment, and that empiricism has no place with it. Photography, 

 on the other hand, has laboured under the disadvantage that, 

 though it is subject to measurement, the factors of exactitude 

 have been hitherto absent. In photography we have to deal with 

 molecules the equilibrium of whose components is more or less 

 indifferent according to the process used ; again, the light em- 

 ployed is such a varying factor that it is difficult to compare 

 results. Perhaps more than any other disadvantage it labours 

 under is that due to quackery of the worst description at the hands 

 of some of its followers, who not only are self-asserting, but 

 often ignorant of the very first principles of scientific investigation. 

 Photography deserves to have followers of the highest scientific 

 calibre ; and if only some few more real physicists and chemists 

 could be induced to unbend their minds and study the theory of 

 an applied science which they often use for record or for pleasure, 

 we might hope for some greater advance than has hitherto been 

 possible. 



Photography has been called the handmaid of Art ; I venture 

 to think it is even more so the handmaid of Science, and each 

 step taken in perfecting it will render it more worthy of snch a 

 title. 



SECTION B. 



CHEMISTRY. 



Opening Address by Sir Lowthian Bell, Bart., F.R.S., 

 F.C.S., D.C.L., M.Inst.C.E., President of the 

 Section. 



It has occasionally been the practice of former occupants of 

 this chair to devote a considerable portion of the Presidential 

 address to the more recent discoveries in chemical science. This 

 branch of learning advances now with such rapid strides and 

 covers so wide a field, that no one who has not made it the 

 business of his life can hope to discharge this duty with even a 

 moderate share of success. 



My immediate predecessor, indeed, discouraged any further 

 attempts in this direction on the ground of the impossibility of 

 doing it justice within the limits of a short discourse, and his re- 

 marks were consequently directed to the best methods of teach- 

 ing the science with which Section B is more directly concerned. 

 I propose this morning to add my testimony to the importance 

 of Dr. Tilden's recommendation by comparing the rate of pro- 

 gress of one of our great national industries as it has been 

 advanced with and without the aid which chemistry is capable 

 of affording. For this purpose I have selected the metallurgy 

 of iron, not only from my greater familiarity with its details, but 

 because, in my judgment, it affiards a suitable example for the 

 object I have in view. 



It is needless to insist on the disadvantage attending the ap- 

 plication of a science to practical work, without a fair knowledge 

 of the principles which regulate its action. At the same time it 

 would be unfair to those who were engaged in the manufacture 

 of iron during the first half of the present century to deny the 

 value of the services rendered to their art, without giving much 

 thought to the laws of Nature upon which their processes de- 

 pended. The work so performed sufficed nevertheless to place 

 the wjrld in possession of the metal in such abundance and at so 

 low a cost, that no engineering works have been delayed on 

 account of the high price of or absence of the required quality 



in the produce of our ironworks during the period in question. 

 On the other hand, it is not to be denied that since the iron- 

 masters have allied themselves with the chemist, they have made 

 more progress in thirty years than their predecessors did in three 

 centuries. 



No one unacquainted with the archaeology of the iron trade could 

 suppose that the colossal furnaces pouring forth their streams of 

 molten metal, followed by the rapid action of the Bessemer con- 

 verter, were the modern representatives of the iron-making ap- 

 pliances of former days. Out of the latter, in a low hearth not 

 larger than a domestic fire-place, often dependent on the wind 

 for their blast, a few pounds of ore were, at a considerable cost 

 for labour, fuel, and waste of metal, converted into malleable 

 iron. By means of a modern furnace in an hour and a half a 

 ten-ton converter can be filled with liquid cast iron, which in 

 twenty minutes may be run into ingots cheaper, stronger, and 

 more malleable than the best wrought iron of our ancestors, or 

 indeed of our own manufacture. 



How out of the small fire of the ancient ironworks the German 

 Stikk-Ofen was evolved is a matter of conjecture. In both, 

 owing to the conditions under which the fuel was burnt, carbon 

 dioxide was largely the product of its combustion. The oxidizing 

 property of this gas was in each the cause of the waste of metal 

 just spoken of. Probably, and for other reasons than avoiding 

 this loss of iron, attempts were made to increase the dimensions 

 of the Stuck- Of en. If this addition were one of limited extent, 

 the smelter would find to his cost that a substance was obtained 

 which no longer possessed the malleable property of that obtained 

 from the lesser furnace. This change would be due to the ab- 

 sorption of carbon, but not in sufficient quantity to constitute 

 that valuable form of the metal known as cast iron. With a 

 material useless for the smith and incapable from its difficult 

 fusibility of being run into moulds, we can understand the delay 

 which took place in the introduction of the blast furnace, which 

 about the middle of the sixteenth century gave to cast iron a 

 recognized and valuable position in the arts. 



In those days there was no very exact science to appeal to, for 

 two hundred and fifty years after the " high furnace " of the 

 Germans and French had been set to work, Fourcroy, in his 

 '* General System of Chemical Knowledge and its Application 

 to the Phenomena of Science and Art," arrived at the conclusion 

 that cast metal was erroneously supposed to be a mixture of slag 

 and iron or a compound of arsenic or manganese and iron. This 

 was written in 1804, in a work of 5000 pages, when he leant to 

 the opinion that Monge and Berthollet were more correct in con- 

 sidering the product of the blast furnace as consisting of iron, 

 oxygen, and carbon. 



When the malleable iron- maker had placed in his hands a 

 material containing, as the pig did, more than 90 per cent, of 

 metal, he found it greatly to his advantage to avoid having to 

 deal with all the earthy matter contained in the ores, for it was 

 the presence of silica and alumina which helped to add to the 

 waste incurred in the old hearths. The object sought for in the 

 old Catalan fires, as they were called, in treating ore was one 

 of a reducing or deoxidizing character, whereas the reverse of 

 this was required when ore was replaced by pig-iron. In the 

 first oxygen had to be removed from the oxide of iron, in the 

 latter oxygen had to be united with the metalloids found in the 

 pig. These were distinctions unknown in the days we are con- 

 sidering, and therefore did not trouble the minds of the iron- 

 masters. In both cases there was a large formation of oxide of 

 iron, and when pig-iron was handed over to the Catalan furnace 

 man, it was the oxide of iron so generated which performed the 

 desired duty, and thus this simple mode of procuring malleable 

 iron remained undisturbed for upwards of two hundred years. 



The discovery which led to the discontinuance of the low 

 blast furnace as a means of procuring iron in its malleable form 

 was that of puddling made by Cort in 1784. In point of fact 

 Corl's process was merely doing in a reverberatory furnace that 

 which was previously effected by means of compressed air. In 

 an economic point of view, however, the difference is great, and 

 its consequences were of immense importance, for to the pud- 

 dling furnace we were first indebted for an ample supply of cheap 

 iron by which, in a variety of well-known ways, the interests of 

 the human race have been so largely promoted. As an indica- 

 tion of the indifference of those formerly engaged in industrial 

 pursuits to the scientific aspect of their calling, may be men- 

 tioned the fact that puddling had been largely followed for 

 upwards of half a century before it occurred to anyone to 

 examine the chemistry of the process. 



