30+ 



NA TURE 



[July 27, 1905 



to the present day. For example, Admiral Sir Edmund 

 Fremantle said that the tactics and strategy at the time 

 of Trafalgar taught lessons which would never die, and 

 Admiral Custance remarked that all the lessons of the 

 past in naval warfare have a bearing on the present day, 

 it being quite immaterial whether vessels were moved by 

 steam or sail. On. the other hand, there are some who 

 hold that the disciples of what has been described as the 

 " teachings-of-history " school carry their reverence for 

 the past to an excessive degree, and that a too blind follow- 

 ing of the tactics and strategy of the great admirals of 

 the past may lead to disaster. Sir Philip Watts, in the 

 course of his paper, pointed out that " steam propulsion, 

 in all its various forms, shell fire, iron and steel armour, 

 steel hulls, breech-loading and rifled guns, torpedoes, 

 mines, high explosives, electrical appliances, and sub- 

 marines " have all been introduced since the day of 

 Trafalgar ; and though he did not press any moral from 

 these changes, his predecessor at the Admiralty was a 

 little more explicit, as it was possible for one no longer 

 trammelled by the rules or etiquette of office to be. Sir 

 William White said in the discussion that while he agreed 

 with Sir Cyprian Bridge that the teachings of history were 

 valuable, it was necessary to allow for changes brought 

 about by time. He did not think such a course was 

 followed on all occasions. 



Mr. Cornish's paper, as a record of the past by a com- 

 petent authority, is one which should prove of considerable 

 value to the student and historian of ship-building. The 

 author did not urge its reading as time was short, and it 

 was accordingly taken as read. 



Colonel Rota's paper was the first taken at the even- 

 ing sitting of Wednesday, July 19. It formed but a part 

 of a very big subject, and was in the nature of an 

 addition to Mr. R. E. Froude's paper on model experi- 

 ments, read last year. The experiments briefly described 

 by Colonel Rota were made with five models at the Royal 

 Italian Dockyard, Spezia. It would be difficult to give 

 the results of the inquiry without going into the whole 

 question, but it may be stated that the author, without 

 attempting to draw any general deduction, has practically 

 concluded that in the unlimited series of forms which may 

 be derived from a given form of hull by changing the 

 vertical and horizontal cross sections scale — provided that 

 the area of cross sections remains constant — there is a 

 range of ratio of beam to draught, very close to that 

 corresponding to the least wetted surface, within the limits 

 of which there is not any sensible variation in the value 

 of the resistance constant, that is, the corresponding 

 E.H.P. There was no discussion on this paper, but Sir 

 William White had written to Mr. Dana, the secretary, 

 endorsing the author's plea for the publication of results 

 of a purely scientific nature. 



The two papers contributed respectively by Mr. Harold 

 Yarrow and Mr. W. W. Marriner were no doubt the chief 

 attraction during the meeting, and the little theatre of the 

 Society of Arts was crowded to its full capacity by those 

 anxious to benefit by the investigations carried out by 

 Messrs. Yarrow and Co. Both papers referred to the 

 same experiments, the authors having been engaged 

 together on the work. Mr. Marriner, as is well known, 

 is the chief of Messrs. Yarrow's scientific staff, whilst 

 Mr. Harold Yarrow is still a student of the institution, 

 and it is worth noting that his paper is the first contri- 

 bution to the Transactions by a student. The data given 

 possesses the merit of being both of scientific and practical 

 interest. It has for some time past been recognised that 

 depth of water has a considerable influence on the speed 

 of steam ships, and Government contractors have lost 

 considerable sums of money through failure to attain 

 speed on the official measured miles. The scientific interest 

 of the subject is unlimited, the problem involving the study 

 of the natural laws governing wave-making and fluid 

 resistance. It is to be hoped that ship builders and ship 

 owners — now Ihey have had placed before them so striking 

 an example of the value of scientific research upon the 

 practical results at which they aim — will do something 

 tangible to help forward an inquiry into the influence of 

 physical laws upon the resistance of vessels progressing in 

 water. It is not creditable to the ship owners and ship 

 builders that they should be beholden to the generosity of 



NO. 1865, VOL. 72] 



a private firm of torpedo-boat builders for information on 

 these points, especially as such information cannot be 

 obtained without the expenditure of several hundreds of 

 pounds. The e.xclusive knowledge of the facts set forth 

 in the two papers would prove a valuable asset to Messrs. 

 Yarrow and, Co. by giving them a distinct advantage over 

 their competitors, and it is therefore more creditable to 

 them that they have made the details public. It is, how- 

 ever, the greatest reproach of all to us, as the leading 

 maritime nation, that Mr. Yarrow should have been under 

 obligation to a German ship-owning firm for the facilities 

 needed to make the investigation complete. Had it not 

 been for the hospitality of their experimental tank offered 

 by the North German Lloyd Company, the valuable in- 

 formation now at the command of ship designers would 

 not have been forthcoming, for there is no tank of the 

 same nature in this country which could have been used. 



The experiments upon which the two papers were founded 

 arose through Messrs. Yarrow and Co. having failed to 

 get the contract speed of 25J knots with destroyers built 

 for the Royal Navy when they were tried on the Maplin 

 mile off the mouth of the Thames. The 'ouilders, 

 anticipating that the limitation in depth of water was 

 accountable for the want of success, surveyed on their 

 own account a mile near Dover, the section posts being 

 placed on the cliffs. Here, in a greater depth of water 

 — 50 feet at low tide — the contract speed was reached, the 

 vessels running a great part of the time in quite deep 

 water outside the Goodwins. It should be explained that 

 the trials last over four hours, and only six runs are 

 made on the measured mile. On these six runs is found 

 the number of revolutions needed to cover a mile, and 

 then by counting the revolutions the distance steamed can 

 be known. -Although the contract was fulfilled, the 

 results were not altogether .satisfactory to the contractors,, 

 and Mr. Yarrow determined to have tank experiments 

 made, testing a model of the destroyer at depths corre- 

 sponding to 20 feet, 30 feet, 45 feet, 60 feet, and 90 feet 

 respectively. The results were shown by diagrams thrown 

 on the screen by the lantern, there being curves for speeds 

 and for effective horse-power at the above depths. The 

 results were somewhat remarkable. Each curve showed a 

 distinct hump, indicating that when a certain speed was 

 reached the power needed for an increased speed rose 

 with enormous rapidity. This, of course, was in accord- 

 ance with previous e.xperience, and it was also to be 

 expected, as shown by the diagram, that the hump would 

 occur at lower speeds with shallower water ; thus at 

 20 feet depth the top of the hump was at about 16 knots, 

 at 4:; feet it was about 20 to 21 knots, and at go feet 

 the steepest part was from 20 to 24 knots. As the depth 

 increased the curve became fairer. 



The interesting feature brought out, however, was the 

 fact that at a certain speed, depending on the depth of 

 water, for a time the power decreased as the speed 

 advanced. Thus in a depth of 20 feet, at a speed of about 

 15J knots, 2000 horse-power was needed ; when the speed 

 had been increased by approximately another knot the 

 power developed was about the same, whilst at 173 knots 

 the demand for power had fallen off appreciably, and it 

 was not until 18 knots was reached that the 2000 horse- 

 power was again required, and after this the curve rose 

 steadily. With a depth of 30 feet the descent of the curve 

 was even more marked, about 2500 horse-power being 

 needed for approximately 175 knots and for 20 knots also. 

 Comparing the powers required for speeds at different 

 depths, we find also some remarkable results. At 18 knots 

 2500 horse-power was needed when the water was 30 feet 

 deep, whilst when it was but 20 feet only 2000 horse- 

 power had to be developed to reach the same speed, thus re- 

 versing the popular idea that the deeper the water the 

 easier the boat would run. Again, at 20 knots, and when 

 the water was 20 feet (and also when the depth was 

 about 30 feet — the two curves approximately coinciding 

 here), 2500 horse-power was needed, but to get the same 

 speed with a depth of 45 feet about 315 horse-power was 

 needed. Passing at once to the higher speed of 26 knots, 

 we find that the highest power is needed when the boat 

 is steaming in deepest water. .After crossing and re-cross- 

 ing each other, the curves for four depths (20 feet, 30 feet, 

 45 feet, and 60 feet) come fairly well together, having got 



