150 REPORT— 1867. 



Strength of Materials. — This subject lias obtained, as its importance deserves, a 

 large share of the attention of the Section. The following are the reports which 

 the Section has received, and the dates of the meetings at which they were read : — : 



1. Mechanical Properties of Metals as derived from frequent Meltings, 1853. 



2. Tensile Sti-ength of Wrought Iron at different Temperatures, 1856. 6. Resis- 

 tance of Iron Tubes to Collapse, 1857, 1858. 4. Eesistauce of Glass Globes and 

 Cylinders to Collapse, 1858. 5. Eflect of Vibratory Action and Long-continued 

 Changes of Load on Wrought-Irou Gu-ders, 1860," 1861. Those five reports are 

 the work of Dr. Fairbairn ; and they contain solutions of questions of the highest 

 importance, practical as well as scientific. The third of them, in particular, con- 

 tains the discovery of a new law in the strength of materials — that which connects 

 the resistance of a flue to coUapse with its thickness, diameter, and length, and the 

 correct application of which is essential to the safety of steam-boilers : it is this — 

 that the intensity of the pressure on the outside of a tube required in order to make 

 it collapse, varies directly as the square of the thickness nearly, inversely as 

 the diauieter, and inversely as the length. The fact of the resistance to collapse 

 vaiyiug inversely as the length had never even been suspected until it was brought 

 to light by Dr. Fairbairn's researches ; and he also pointed out the remedy for that 

 cause of wealmess in the use of stifi'ening rings for dividing the length of the tube 

 into intervals of a length consistent with safety. The fifth of those reports con- 

 tains the first detennination, with any approach to precision, of fha factor of safety 

 in engineering sti-uctures of wi'ought iron. (The corresponding factor for cast 

 iron had been determined by the Parliamentary Commissioners on the Application 

 of Iron to Railway Sti-uctm-es.) It had long been well known that the load which 

 structiu-es will bear with safety when repeatedly removed and replaced, and accom- 

 panied with vibration and rapid motion, is veiy much less than the load required to 

 break the sti-ucture at once ; but the ratio which the latter load bears to the former, 

 called the "factor of safety," had never, until these researches were made, been 

 fixed according to any principle based on a foundation of experiment. 6. Adap- 

 tation of Suspension Bridges to Railway Trains, 1857, 1858, by Mr. ^''ignoles. 

 Along with this report there should be mentioned, as having contributed^to the 

 solution of the same question, a paper by iMr. P. W. Barlow, read in 18(50. The 

 researches of both these authors relate to the means of enabling suspension bridges 

 to bear heavy travelling loads, by the aid of stifi'ening framework. 7. Strains in 

 the Interior of Beams, 1862, by the Astronomer Royal. 8. Streng-th of Materials 

 in Ii-on-ship-building, 1865, by Dr. Fairbairn. Next follow a series of reports of 

 very high interest, relating to the application of materials to the art of national 

 defence._ 9. Durability and Efficiency of Artillery, 18-55; a provisional report by 

 a committee, containing suggestions for researches. 10. Resistance of Ii'on Plates 

 to Pressure and Impact, 1866, by Dr. Fairbairn. 11. Mechanical Properties of 

 Iron Projectiles at High Velocities, 1862, by Dr. Fairbairn. 12. Rifled Guns and 

 Projectiles,^ 1862, by Mr. Aston. 13. Penetration of Armour-plates and Iron-clad 

 Ships, 1866, by Captain Noble. It is unnecessary to enlarge upon the value and 

 interest of the results recorded in the last-mentioned report, which must be fresh 

 in the recollection of the members, having been read at Nottingham, and printed in 

 thelast volume of Reports. Those results constitute the gTeatest step in advance 

 which has_ hitherto been made towards acciu-ate knowledge of the quantity of 

 work required in order to pierce a given target with a given projectile, and the 

 quantity of powder required in order to do that work. 14. Mechanical Properties 

 of the Atlantic Telegi-aph Cable, 1864, by Dr. Fairbairn. 



Motive Pou-er. — The obtaining of motive power by means of steam has to a great 

 extent been considered by committees of the British Association in connexion with 

 the propulsion of vessels'; and so far it comes under the head of steam navigation, 

 a subj ect to which I shall presently refer more fiiUv. The followina' are the Reports 

 relating specially to motive power :— 1. On the ^'oftex Water-Wheel, 1852, bv Prof. 

 James Thomson. 2. On Water-Pressure Machinery, 1854, by Su- W. G. Armstrong. 

 These two reports contain valuable information as to two important classes of 

 hydraulic prime movers. 3. On the Density of Steam, 1859, 1860, by Dr. Fair- 

 bairn and Mr. Tate. These communications were not printed amongst the Reports, 

 but only in the ' Proceedings ' of this Section, being merely abstracts of researches 



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