166 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



M 



AY, 



short epitapli formerly referred to, I was unable to find ; but upon one of the 

 flat stones on the floor near the altar I observed the following inscription : — 

 Gonzali Fernandez de Cordoba, 

 qui propria virtute 

 Magni Ducis nomen 

 propriuni sibi fecit, 

 Ossa, 

 perpetua." tandem hici restituenda, 

 huic interea loculo condita sunt, 

 Gloria minime consepulta. 

 The epitaph appeared to mc to be happily expressed, and reminded me of 

 the brief and fine eulogiuni of Cervantes, introduced at the place where the 

 innkeeper brings to the curate and barber his library of three books, two of 

 which were condemned to the flames, but the third was worthy of immortal 

 honour, being the history of Oonzalvo Ferdinand, " el qual por sus muchas y 

 grandes hazanas merecio ser llamadode todo cl nuindoGran Capitan, renom- 

 brc famoso y claro, y del solo merecido." 'While our party were in the chapel, 

 a number of the soldiers from the convent had followed us from curiosity, 

 and wondered what we found to interest us in its bare and desolate aspect. 

 In passing through Spain, the traveller at every step meets traces of its former 

 glory and splendour, and cannot help contrasting these with the present de- 

 graded state of the country anil people. The contrast came vrith new force 

 to me while in the chapel of San Geronimo; recalling the brave veterans of 

 the wars of Naples and Flanders, then the finest soldiers in Europe, and com- 

 paring them with the wretched troops of modern Spain, specimens of which 

 were now gaping and jesting over the remains of the Great Captain. 



PORTER AND GO'S PATENT ANCHORS. 



One of the most interesting experiments, and one which cannot fail to 

 prove of immense advantage to the" navy, and the merchant service, took 

 place on Monday in the presence of Captain Phipps Hornby, C.B., superin- 

 tendent of Her ilajesty's Dockyard, Woolwich, and a number of nautical 

 gentlemen. One of Porter and Co.'s patent anchors having been previously 

 placed on the testing frame, an immense power was applied by an hydraulic 

 machine invented by Bramah and Son, and the anchor weighing 5 cwt. 2 qrs. 

 24 lb., which would have been considered safe according to the adopted test 

 of 8| tons, actually sustained additional strains until it reached 20J tons be- 

 fore it gave way under the application of that immense power — nearly 2^ 

 times greater than would ever be required under ordinary circumstances. .\ 

 second anchor, weighing 5 cwt., was afterwards placed on the testing frame, 

 and the power having been appHed, it sustained a strain of 21 J tons, given 

 by jerks, before it gave way, although it would have been considered perfectly 

 safe if it had stood 8} tons. There was another anchor by the same patentee 

 on the spot, of still larger dimensions, but the experiments with the other 

 two were so satisfactory that it was not found necessary to prove its 

 capabilities. It appears strange, and yet it is evidently the fact, that the 

 more simple the construction of any article is, there is the greater certainty 

 of its success. The principal dift'erence betwixt this anchor of Porter and 

 Co., and those at present in use, is a projection on the outside of the fluke, 

 which enables it to catch hold of the most difficult ground, and ensures its 

 obtaining a firm hold and double power by the upper fluke descending on the 

 shank, and acting as a fulcrum in the most effectual manner. By the kind- 

 ness of Captain Denham, of the MariBC Surveyor's department, we have been 

 enabled to give the following details of the advantages of this anchor. — " It 

 is almost impossible to foul it. It bites quickly into the most stubborn 

 ground. It holds on the shortest stay peak. It cannot well lodge on its 

 stock-end, It presents no upper fluke to injure the vessel herself or others 

 in shoal water. It cannot injure vessels' bows when hanging cock-bill, as 

 merchant vessels find a convenient practice. It is not so likely to break off 

 an arm or part in the shank as anchors with fixed flukes do, because the con- 

 struction of these arms can be of continuous rod-iron, and the leverage is so 

 much nearer the ring, owing to the pea of the upper ring closing upon the 

 shank. It is a most convenient anchor for stowing on board, on a voyage, 

 as the flukes can be easily separated, and passed into the hold ; it can as 

 easily be transported by two boats, when one would be distressed with the 

 whole weight. Several of the officers who witnessed the experiments stated 

 their intention of applying to the Admiralty for anchors on this construction, 

 as they were so satisfied of tlieu- advantages." — Times. 



PROCEEDINGS OF SCIENTIFIC SOCIETIES. 



INSTITUTION OF CIVIL ENGINEERS. 



Jan. 12. — JosHu.\ Field, V. P., in the Chair. 



" Remarks on the comparative advantages of lontj and short Conttectim 

 Rods, and low/ and short stroke Engines." By John Seaward, M. Inst. C. E. 



The author commences the c'omraunication with a description of the engines 

 first placed on board the Steam Frigate, " The Gorgon." 



The engines are constructed on the principle of " direct action." that is, the 

 power is communicated directly from the piston to the crank, without the 

 intervention of side levers, and the other parts usually employed in the con- 

 struction of marine engines ; this is one leading feature. Another is, that 

 the main shafts are placed directly over the centre of the cylinder ; and as 

 these shafts are carried by strong frames and wrought iron columns standing 

 upon the cylinders, the force of the engines is confined between the cylinders 

 and the frame, and thus isolated from the sides of the vessel. Other advan- 

 tages accruing from this construction are, in the author's opinion, a saving of 

 space and weight, the al)sence of the Wbration resulting from the action of 

 the side levers, and a more efficient application of motive power, arising from 

 the simplicity of the construction and diminution of friction. 



Two main objections have been urged against this system — 1st, that the 

 shortness of the connecting rod causes a loss of effect ; and 2nd, that the 

 shortness of the stroke is a disadvantageous application of the power of 

 steam. 



The arguments in support of these objections are combated at considerable 

 length. With reference to the alleged loss of power by the use of the short 

 connecting rod, it is argued, that as no arrangement of long or short rods or 

 levers could create power ; so no arrangement of similar parts could be pro- 

 ductive of loss of power. A geometrical investigation of the force actually 

 exerted on the crank by long and short connecting rods is then given, and 

 the result deduced is, that by adding together the whole of the force exerted 

 by the two kinds of connecting rods respectively, during one entire rotation, 

 they both give the same actual amount ; thus proving, that no loss arises 

 from tlie use of the short connecting rod. 



It is admitted, that there is some increase of friction on the journals of 

 the connecting rod joints, but this occurs only at tne extreme angles ; some 

 allowance is also to be made for the increased angular motion about the 

 lower joints of the rod, but they are not collectively of sufficient importance 

 to be considered as any objection in practice. 



The calculations given are under the approval of Professor Airy, who thus 

 •expresses himself: — " The greatest force of the ' Gorgon' engines (when both 

 cranks are below the horizontal line) is greater than the greatest force with 

 common engines, but the least force is not less than the least force with com- 

 mon engines." 



The whole power, in a complete revolution of the crank, is the same in 

 both. 



That a long stroke engine, under certain circumstances, may be more ad- 

 vantageously employed than a short one, is admitted ; but considering the 

 steam engine per se, it is argued, that the latter possesses no advantage over 

 the former. 



In two engines of equal power, equally well constructed, the length of the 

 stroke being respectively eight feet and four feet, the cylinder of the latter 

 having double the area of that of the former, making the same number of 

 revolutions per minute, and having the steam passages and valves of the same 

 area, it is clear, that the mechanical action of the steam must be identical, 

 because the same volume of steam will produce an equal mechanical effect, 

 whether it be introduced into a long narrow cylinder, or into a short wide 

 one ; setting aside the effect of working expansively, which, however, is not 

 at all affected by the shortening of the cyhnder : (or it is just as practicable 

 to shut oflf the steam at one-half, one-third, or one-fourth of the stroke of a 

 short cylinder as of a long one. 



The most essential differences between these two engines must be in the 

 relative amount of friction, and of radiation of heat from the cyUnders and 

 passages. 



In a well made engine four-fifths of the friction is due to the packings of 

 the piston, air-pump bucket, and stuffing boxes, and about one-fifth to the 

 gudgeons, crank pin, and other moving parts. The friction of the piston 

 packing is as the circumference multipUed into the space through which the 

 piston travels, and into the depth of the packing ; therefore in a cylinder 30 

 inches diameter, 8 feet long, the friction of the packing will be as 24. while 

 in a cylinder of 42-4 inches in diameter, 4 feet long, it will be only as 17. 



The same train of reasoning is extended to the other moving parts, and 

 shows that if the total friction in the short stroke be 100, that of the long 

 stroke engine will be 123. 



The radiation of heat from the cylinders will be as the relative areas of 

 surface, which is less in the short stroke than in the long. 



An examination of the comparative friction of the moving parts of steam 

 engines is entered into ; rules for computing, and tabular results are given ; 

 and the author concludes by observing, that although the relative dimensions 

 selected as examples are uncommon in England, they are not so in America, 

 where pistons of marine engines frequently travel at the rate of three hundred 

 to four hundred feet per muiute. It is contended that the speed of the piston is 

 immaterial, provided the engine be well proportioned to the speed ; at the 

 same time bearing in mind that a slow speed will he more favourable for the 

 easy and pleasant working of the engine, and for durability. The paramount 

 objects to be aimed at in the construction of marine engines are, the greatest 

 saving of fuel, space, and weight, and the durability of the machine ; and as 

 the question is not whether the stroke should be eight feet or four feet, but 

 relates to a diminution from the present length of seven feet to probably six 

 feet, it is contended that the form of the " Gorgon "engines oflfers consider- 

 able advantages in the points treated of, independently of the positive dimi- 

 nution of weight and space, which forms no part of the immediate inquiry. 



.\ drawing of the " Gorgon" engines accompanied the commiuiication. 



