876 



THE CIVIL ENGINEER AND ARCHITECT S JOURNAL. 



[August, 



Tensile 

 strength. 



In timber 1900 



Cast iron 158 



Glass (plate antl crown) . . 123 

 Stone and marble 100 



Ratio of mean 

 Transverse fransile to one 

 strenRtli. strong force. 



85-1 1-55 



10-8 1-66 



10- 1-78 



9-8 1-105 or 1-89, 



taking the 

 hardest only. 



The ratio of the crushing force to the transverse force is nearly the same in 

 glass, stone and marble, including the hardest and the softest kinds. Hence 

 if we know the transverse strength or the crushing strength in any of these 

 bodies, we may predict the other ; and, as glass and the hardest stones 

 resist crushing 'with from seven to nine times the energy that they do being 

 torn asunder, we may get an approximate value of the tensile force from the 

 crushing force, or t'ice versa. These results render it probable that the 

 hardest bodies, whether cast iron, glass, stone, or marble, admit of certain 

 atomic displacemeats, either in tearing asunder or crushing, these displace- 

 ments being in a given ratio to each other, or nearly so. In future calcula- 

 tions as to the strength of bodies, the crushing strength ought to be made 

 the fundamental datura, which I have recently done, for the reasons shown 

 in this notice. The ratio of the transverse strength to the crushing strength 

 is greater in cast iron than in glass, marble, and sandstones, arising from the 

 ductability of that metal. The necessity of enlarged inquiries in these matters 

 will he seen, when it is reflected that calculations of the transile strength of 

 cast iron, or marble, or stones in general, made from the transverse strength 

 by the modes used by Tredgold, Navier, and others, give the transile strength 

 twice or three times as great as it ought to be. 



The Chairman said the section was greatly indebted to Mr. Hodgkinson 

 for his very interesting communications. Those experiments had attracted 

 much attention from scientific men, and the Royal Society had presented him 

 their medal for a former paper on this subject. [We may here mention, that 

 this communication was only some portion of a more full and perfect paper, 

 to be read before the Royal Society ; such communication being now made 

 onlv as would not preclude Mr. Hodgkinson from laying the more complete 

 results before that society.] He might also express the opinion of practical 

 men, that no experiments, either as to e.xtent, care, or accuracy of observa- 

 tion, gave results at all comparable in point of value with those of Mr. 

 Hodgkinson, who, he hoped, would have the time and inclination to pursue 

 his experiments to a greater extent. There were no results in practical 

 science of greater importance than those which showed us the strength and 

 stability of materials. In the structure of buildings, upon which the comfort 

 and wealth of so many individuals depended, and in other structures in 

 engineering operations— an ignorance of the important facts arrived at by 

 Mr. Hodgkinson had, in many cases, led engineers to make structures dis- 

 proportionatelv strong or weak ; in the one case causing unnecessary waste 

 of materials and unnecessary expense, in the other periling the stability of 

 the structure, and the safety and lives of those within it. 



The Rev. Dr. Peacock (Dean of Ely) then made an oral communication 

 " Upon the report of the fOMinlsxioner.i for the restoration of lost standards 

 of weights and measures, and upon their proposal for the introduction of a 

 decimal system" (during which communication Sir Wilhara Hamilton took 

 the chair). After stating that the imperial standards of weights and measures 

 (the yard, the lb., the gallon, and several of their multiples) had been lost 

 in the fire vs-bich destroyed the two Houses of Parliament, he said that a 

 commission (of which he was a member) had been appointed, to report on 

 the best means of restoring these standards. He noticed the proceedings of 

 a former commission, on whose recommendation the act of the 5th Geo. IV. 

 had been passed, declaring the imperial standards of weights and measures, 

 and prohibiting all others to be used, and pointed out the erroneous data on 

 •which that former commission had fixed the standard yard ; by which data, 

 therefore, the present commission did not recommend its restoration, but 

 rather to take the extant copies of it, especially the one in the care of Mr. 

 Trancis Baily, as the authority upon which the new standard yard should be 

 ■formed. The commission also recommended to the government that the 

 standards of length and weight should be independent of each other, wiiich 

 was not the case before. The standard pound weight was Troy weight 

 (5780 grains), though the pound avoirdupois (7000 grains) was used through- 

 out the country, in the proportion perhaps of 10,000 to one of Troy. The 

 commission recommended the standard pound to be the representative of the 

 avoirdupois, and not (as before) of the Troy pound ; that, hereafter, the use 

 of the Troy pound should be abohshed, except for a very limited number of 

 transactions, and that the avoirdupois pound should be considered as the 

 standard pound of Great Britain. They reconimeuded that measures of 

 capacity should be determined by measures of weight— by far the most con- 

 venient method, inasnuicb as weighing was a much more accurate operation 

 than, for instance, the formation of a perfect cube. The commission also ven- 

 tured to recommend strongly some alterations in the coinage, and the systems 

 of weights and measures, arising out of a more extensive introduction of the 

 decimal scale. The nearly unanimotis determination of the commission was, 

 that any attempt to interfere materially with the primary units of the 

 coinage,' weights, and measures, in ordinary use, would produce such confu- 

 sion and bad consequences in the ordinary transactions of life, that they 

 woidd adhere strictly to all those primary linits, viz., the pound sterling of 

 our coinage, the yard, in the measure of length (and also the foot, for there 



were two primary units in this measure), the acre, in the measure of areaSF 

 the gallon, in the measure of capacity, and the imperial pound in the measure 

 of weight. As the coinage must necessarily be the basis of any changes 

 leading to the more extended adoption of a decimal scale— taking the pound 

 sterUn" as the primary unit, they proposed to introduce a coin of the value 

 of 2*. "(one-tenth of the pound); another, either silver or copper, of one- 

 tenth of 2s. (or 2d. and a fraction) which might be called a cent (the 

 hundredth of a pound) ; and the thousandth part of the pound sterling, or 

 nearly the value of our farthing (of which there are 960 in the pound), 

 which new coin it was propose<l to call a jnillet (from thousandth). The 

 difference in the value of tlie copper coinage was less important, as it was 

 merely a representative coinage, aud had not an approximating intrinsic 

 value,' hke the gold and silver coinage. For the proposed coin of 2s. various 

 names had been suggested, as Victorine, rupee, or florin ; it being not much 

 different from the vatue of some of the rupees of the East Indies, or the 

 florin of the Continent. Under this new decimal scale the shilling would be 

 retained, and also the sixpence (but the latter under another name, more 

 representative of its value). For the half-crown would be substituted the 

 2s. or Victorine. The very rev. gentleman dwelt at some length on the 

 advantages of this change, in the extensive money transactions and accounts 

 of bankers and merchants ; in the Bank of England, for instance, where a 

 thousand clerks were employed, where it would greatly facilitate the opera- 

 tions of calculation and book-keeping. Thus, discarding millets (for bankers 

 now excluded the subdivisions of a penny in their accounts), the sum of 

 .€17 3 Viclorines, 7 cents, would be represented at once by 17-37 ; only two 

 places of decimals, instead of as now in pounds, shillings, and pence. He 

 showed how the princiole was applicable, with still greater advantage, in 

 cases of weights and measures (where the scale was now most anomalous 

 and absurd). Suppose the rental or value of 30-64 acres of land to be 

 required, and that the land cost £09 3 Viclorines, 4 cents, an acre. The 

 reduction in common arithmetic was one of very considerable labour, difli- 

 cultv, and time. Indeed, if this decimal system were adopted, the labour 

 of teaching arithmetic to school boys would be reduced nearly one half. But 

 bv this plan (as the rev. doctor showed), the result might he obtained in five 

 li'nes of decimals, containing only 21 figures. As to weights, the most 

 extensive change recommended by the committee would be to introduce the 

 uniform weight of 10 lb. to the stone, instead of the varieties of 8 lb. in 

 some, and 14 1b. or 16 1b. in other parts of the kingdom; the hundred 

 weight to be called centna (a German term). There were all the changes 

 proposed in weights, the commission not wishing to interfere with the sub- 

 division of the pound, which admitted of four subdivisions into 8 oz., 4 oz., 

 2 oz., and I oz. The pound and ounce would remain, therefore, exactly the 

 same' as at present. As to the measure of length, the commission thought 

 it too violent a change to alter all the milestones ; but there would be no 

 difficulty (with reference to the standing orders of parliament, in railway 

 matters', &c.) to introduce the measure of 1000 yards, which might be called 

 a mih/ard. However, the commission made no recommendations as to no- 

 menclature, leaving that to the legislature. Thus the changes proposed to 

 be introduced, not onlv to ensure a decimal coinage, but a decimal subdivision 

 of weights and measures, were by no means of that formidable and appalling 

 character which manv persons supposed they must of necessity possess. 



On the use of Beton and Concrete in the construction of Breakwaters. 

 Mr. Vignoles called the attention of the section to the works now going 

 on'at Algiers, in the formation of tafakwaters by the use of concrete, under 

 the direction of M. Poirel, where We said a shelter had already been made 

 for 15 sail of the line, at an expense, even under all the difliculties presented 

 by the circumstances of that -country, of about 20s. per cubic yard ; and he 

 had no doubt that in this country, in any situation where a good hydraulic 

 Ume could readilv be procured, the expense would not exceed 10s. per cubic 

 yard. Some very extensive works of the same kind had also been executed 

 at Marseilles. Jlr. Philip Taylor, of Marseilles, in confirmation of Mr. 

 Vignoles, mentioned several instances in which concrete was used in that 

 neighbourhood, with the greatest success. He stated that bc'ton was a ma- 

 terial much used in that vicinity, though scarcely known m England. It was 

 composed of one part of ground brick, and two parts of lime. Mr. Smith, 

 Jlr Fairbairn, and several other gentlemen, expressed their opinions as to the 

 value of concrete, and its applicability to a variety of purposes to which it 

 was not commonly applied. 



Mr. Scott Russell's Inde.rfor the speed of Steam Vessels. 



Mr. Russell stated, that his index of speed was founded on the well-known 

 dvnamical fact, that if an aperture were made in the lower part of a vessel 

 containing water, and a stream were allowed to issue from it against an aper- 

 ture in another vessel containing water, the force of the current would keep 

 the water in the second vessel at the same height as in the vessel from which 

 the current issued. It would follow, from this principle, that if a vessel were 

 passing through the water at a speed equivalent to that of the current produced 

 by a given head of water, the resistance would raise water m a tube inside 

 the vessel, hut subjected to the action of the external fluid. Mr. Russell then 

 proceeded to detail the particulars of the invention to which he had applied this 

 principle, bv passing a tube through the bow of the vessel, and carrving it along 

 the flooring to the centre of gravity of the vessel, where it terminated in a 



