5IO 



NA TURE 



[SeI'TEMBER 2 2, I. 



as to which, as I have said, Bristol is interesting to engineers, 

 there are one or two other matters of history which appeal 

 to Section G in this locality. In the first place, Bristol was 

 the birthplace of the Great Western Railway. I. K. Brunei, 

 its engineer, had previously, by public competition, been 

 selected to span the gorge at Clifton by a suspension bridge 

 of the then almost unrivalled span of 702 feet. Again, 

 under the influence of Brunei, Bristol became the home of 

 the pioneers of Transatlantic steamships, and the story of 

 the initiation of the enterprise is thus told in the memoirs 

 of his life. In 1835, at a small convivial meeting of some of 

 the promoters of the Great Western Railway, some one said, 

 " Our railway to Bristol will be one of the longest in England," 

 and Brunei exclaimed, " Why not make it the longest line of 

 communication in the world by connecting it with New York 

 by a line of steamers?" Out of this grew the Great Western 

 steamship, and the history of the enterprise and of its success is 

 too well known, at least here, to require any allusion to the 

 steps by which it was brought about. Suffice it to say that, in 

 spite of much discouragement, the Great Western — of the then 

 unexampled size of two thousand three hundred gross tons, and 

 with engines of unparalleled power— was launched at Bristol in 

 1837, and ran successful and regular voyages till 1857, when 

 she was broken up. 



In Section G there are many who can appreciate the diffi- 

 culties of such a new departure as the Great Western steamship, 

 even if they had been confined to the design and study of a 

 vessel and engines of unprecedented size ; but it is not easy to 

 realise the anxiety and trouble caused by the dictum of a man of 

 science so universally admired as Dr. Lardner, at the meeting 

 of the British Association in this city in 1836, that the whole 

 idea of ocean navigation on voyages as long as from Bristol 

 to New York was at that epoch an abstract impossibility. 



In these days of criticism of the past, often involving the re- 

 habilitation of individuals, it is interesting to note that Dr. 

 Lardner's part in condemning beforehand the construction of 

 the Great Western steamship and the ideas on which she was 

 designed has been of late years unduly minimised. It has been 

 said that all Dr. Lardner meant was to express a pious doubt 

 as to the commercial prospects of ocean navigation. I have 

 carefully read the Proceedings of the time, and I am brought to 

 the conclusion that his words and writings will admit of no such 

 interpretation. Dr. Lardner's views, arrived at after calcula- 

 tion and reasoning, were precisely expressed and boldly and 

 honestly enunciated by him. The words of the discussion here 

 appear not to have been preserved, but in an elaborate article in 

 a Quarterly Review in 1837, which is, I believe, admitted as 

 having been written by Dr. Lardner, he said, " that in proportion 

 as the capacity of a vessel is increased, in the same ratio, or nearly 

 so, must the mechanical power of the engines be enlarged and 

 the consumption of coal augmented." He based his views that 

 success was impossible on principles which he supposed to be 

 sound, but which were, in fact, assumptions — viz. that the re- 

 sistance to the progress of a ship varied directly with her cap- 

 acity, that a certain number of tons of coal were required per 

 horse-power for the voyage across the Atlantic, and that, this 

 being so, enough fuel could not be carried in a ship, however 

 large she might be made. 



Brunei, on the other hand, contended that Dr. Lardner's 

 views were fundamentally erroneous ; for that, whereas the 

 capacity of a ship increased in the ratio of the cube of her 

 dimensions, the resistance to her progress varied more nearly as 

 the square. Thus, by adopting a proper length, beam, and 

 draught, a ship would not only carry coal for the journey to New 

 York, but be commercially successful in respect of cargo and 

 passengers. 



It is interesting to note that 9 lbs. of coal per indicated horse- 

 power per hour (as compared with our present i^ to 2 lbs.) was 

 the approximate coal consumption which was more or less 

 accepted by both sides in tlie controversies of 1836 and 1837. 



We know now that the resistances encountered by a ship are 

 not merely dependent on her dimensions, but comprise wave- 

 niaking at various speeds, bringing form and proportion of 

 dimensions largely into the necessary calculations ; but I want to 

 point out that the line of divergence of the different views of 

 Lardner and Brunei was sufficiently precise and quite crucial. 

 It is true that Dr. Lardner, in later criticisms of 1837, re- 

 treated somewhat from his position of 1836, introducing more 

 of the commercial aspect of the case and stating that no steam 

 vessel could make profitable voyages across the Atlantic, at 



NO. 1508, VOL. 58] 



least until marine engines were immensely improved ; but, 

 even so, it seems clear that the fundamental matter at issue in 

 1836 and 1837, the period of Dr. Lardner's active criticism, was 

 the question of the resistances increasing in the same ratio as 

 the capacity. The results of these ex cathedrA statements by 

 Dr. Lardner about the Great Western, then in process of being 

 built, must have caused great anxiety to the promoters and much 

 preliminary distrust of the ship on the part of the public. They 

 were, unquestionably, honestly arrived at, however much they 

 were due to reasoning on unascertained premises, and this latter 

 is the reason for my venturing now to refer once more to them. 

 As a matter of fact, the ship started from Bristol in 1838, and 

 arrived at New York in fourteen days with 200 tons of coal in 

 her bunkers. 



Let me remind you of another somewhat similar instance of 

 the way in which the anxieties of engineers have been unnecs- 

 sarily increased and public alarm gratuitously, though honestly, 

 aroused. When the designs of the Forth Bridge — of which the 

 nation, and indeed the world, is proud — had been adopted both 

 by the Railway Companies who were to find the capital and by 

 Parliament, a most distinguished man of science — the then 

 Astronomer Royal — came to the conclusion that the engineers 

 had neglected certain laws which he enunciated respecting the 

 resisting power of long struts to buckling, and that the bridge 

 ought not to be constructed, as he considered that, to use his 

 own words, " we may reasonably expect the destruction of the 

 Forth Bridge in a lighter gale than that which destroyed the Tay 

 Bridge." AH this was stated no doubt from a strong view of 

 public duty, in a letter to a public newspaper, though subse- 

 quently and frankly withdrawn. If the bases of his calculations 

 were right, the conclusion might have been correct ; but the 

 fact was, that there was no foundation worthy of the name for 

 the reasoning. Again, another distinguished mathematician 

 publicly criticised the Forth Bridge with equal vigour, basing 

 his views that it was fundamentally incorrect on another set of 

 equally erroneous assumptions, maintaining again that it should 

 not be permitted, because he proved by reasoning on those 

 assumptions that it must be absolutely unsafe. 



Once more, in ship-building, until Mr. William Froude, some 

 years prior to 1875, made his experiments by means of models 

 on the highly difficult and otherwise almost insoluble causes of 

 the retardation of ships and their behaviour in waves, beginning 

 at the beginning, taking nothing for granted, and eliminating all 

 elements of possible errors, little or nothing was known of the 

 laws governing these questions. Laws had been laid down by 

 high authorities as to the causes of retardation of ships, many of 

 which, in fact, were not true, while some of the assigned causes 

 were non-existent and some real causes were unrecognised. Mr. 

 Froude was told that no information could be learnt from experi- 

 ments on models which would be applicable to full-sized ships, 

 and that ships must continue to be designed and engines built 

 on data which, scientifically speaking, were assumptions. The 

 outcome has been that Mr. Yxovi^€% a priori depreciated experi- 

 ments with models have solved most of the questions relating to 

 that branch of naval architecture ; and at the present time every 

 ship in the Royal Navy, and not a few in the merchant service, 

 are designed in accordance with the data so gained. 



Another example of hasty generalisation occurs to me, and 

 that is on the important question of wind pressure. Tredgold, who 

 undoubtedly was one of the soundest of engineers, laid down in 

 1840 that a pressure of 40 lbs. per square foot should be provided 

 for ; reasoning, no doubt, from the fact that such a pressure had in 

 this country been registered on a wind gauge of a square foot or 

 less in area. As a consequence, he assumed that the same force 

 could be exerted by the wind on areas of any dimensions. Thus 

 roofs and bridges, wherever any calculations of wind pressure 

 were, in fact, made, were designed for a pressure of 40 lbs. per 

 square foot of the whole exposed surface, and under the alarm 

 caused by the fall of the Tay Bridge in 1879, the piers of which 

 were not probably strong enough to resist a horizontal pressure 

 of one-fifth of such an amount, a further general assumption was 

 made, and railway bridges throughout the kingdom were ordered 

 by the Board of Trade in 1880, acting no doubt on expert advice, 

 to be in future designed, and are designed to this day, to resist 

 56 lbs. of horizontal wind pressure on the whole exposed area 

 with the ordinary factors of safety for the materials employed, as 

 if such horizontal strain were a working load. 



It had, for a long time previously to this order of Government 

 being issued, been suspected that these small-gauge experiments 

 were untrustworthy, and subsequent experiments at the Forth 



