August 12, 1909] 



NA TURE 



203 



formula; since brought forward give a more accurate 

 measurement. It is, of course, not fitted for use 

 with racing motors, in wliich everything in design is 

 sacrificed to piston speed, high mean pressure, and a 

 sufficient endurance to last through a few races. For an 

 engine having 4-inch cylinders the Royal Automobile Club 

 formula gives a rating of 25-6 horse-power, which is about 

 the brake horse-power that a normal engine of this size 

 would yield when driven at a normal speed. Racing 

 motors of this size have, however, given almost, if not 

 quite, 100 horse-power, and even if it were possible to do 

 so it is a question whether it is worth while to search 

 out a formula which would embrace such divergent prac- 

 tice and conditions of operation. The Royal Automobile 

 Club formula corresponds to combining a piston speed of 

 1000 feet per sec. with a mean pressure of 672 lb. per 

 square inch. Before it can be revised a complete series 

 of careful experiments on engines of sizes ranging from 

 2 inches to 10 inches should be carried out. 



In the succeeding article the writer proposes to discuss 

 details of the recent mechanical improvement of the 

 internal-combustion engine in relation to the theoretical 

 investigations already discussed. 



H. E. WiMPEKlS. 



A 



CONFERENCE OF ENGINEERS AND SHIP- 

 BUILDERS AT GLASGOW. 



JOINT summer meeting of the members of the 

 Institution of Engineers and Shipbuilders in Scot- 

 land and of the North-east Coast Institution of Engineers 

 and Shipbuilders was held in Glasgow on August 4, 5, 

 and 6. It is of interest to note that, although a large 

 number of works and shipbuilding yards was thrown 

 open to visitors, no works in which .Admiralty work is 

 under construction were included. This arises from the 

 firms concerned paying respect to the wishes of the 

 .Admiralty that as much secrecy as possible should be 

 observed regarding the details and progress of Govern- 

 ment work. Wednesday and Thursday mornings were re- 

 served for the reading and discussion of papers, of which 

 we give brief extracts. 



Sir Andrew Noble contributed some notes on the history 

 of propellants. Perhaps the easiest way of show'ing the 

 striking difference-between the old gunpowders and some 

 of the modern propellants is to quote two tables given 

 by the author. As both the units of heat and the quantity 

 of gas vary considerably, depending on the pressure under 

 which the propellant is exploded, the author has taken 

 the transformation approximately at the pressures at which 

 the propellants are generally used in guns. 



Older PropeUants. 



Pebble R.L.G. F.G. "^""'."S Bp^v.\!h 



powder powder 



Volume'! of eas 278 274 26? ;6o 2-54 



Unifiofheat 721 726 738 ^17 767 



Comparative energy 200,438 198,924 194094 186,120 179,478 



Modern PropeUants. 



Cordi'e, I'anan M.D. Norwe- Nitro- Norwe- 



Mark I. ballistlle cordite gian 167 cellulose gian 165 



Vo'uniei of gas ... S75'5 Bio's 9i3"5 ^99 9 934'o 909*9 



Units of beat ... 1246*0 i305'o io3o'o 10055 O24'o 935'5 



Comparative energy 1,090,873 1,057,703 940,905 904,850 £63,016 851,212 



It will be seen from the tables that the comparative 

 energies of the modern explosives are more than four 

 times as great as those of the older propellants. 



.\s regards the serious question of erosion, in the case 

 of very large guns it is important to remember that, 

 xvhile the surface of the bore subject to the more violent 

 erosion increases approximately as the calibre or a little 

 more, the charge of the propellant required to give to 

 similar projectiles the same maximum velocity increases 

 as the cube of the calibre. Consequently, unless special 

 arrangements as to the projectile are made, or other means 

 adopted, the life of the largest guns before re-lining must 

 be short when compared with that of smaller guns. 

 .Attention should be given to the best method of reducing 

 erosion when very large charges are used, either bv lower- 

 ing the temperature of explosion or possibly by introducing 

 some cooling agent with the charge. 



NO. 2076, VOL. 81] 



The author has tested the capacity for erosion of several 

 explosives, and has found these to vary considerably, but 

 all give similar results with varied charges. Thus the 

 erosion due to one three-quarter charge was less than 

 that of a full charge, but two three-quarter charges gave 

 more erosion than one full charge. Two half charges gave 

 less, but three half charges gave more, erosion than one 

 full charge. These experiments controvert the statement 

 which has been made frequently that the erosion due to 

 four three-quarter charges, as also that due to si.xteen 

 half charges, are equivalent to the erosion due to one 

 full charge. 



A paper on the trials and performances of the S.S. 

 Otaki, by Engineer-Commander W. McK. Wisnom, R.N., 

 is of interest in view of this vessel being the first merchant 

 vessel fitted with a combination of reciprocating and 

 turbine machinery. The Otaki was built by Messrs. 

 Dennv, of Dumbarton, and delivered in November, 1908. 

 She has since completed a voyage to New Zealand and 

 back, and is virtually a sister ship to the twin-screw 

 vessels Orari and Opawa, fitted with reciprocating engines 

 and constructed by the same builders. .AH three vessels 

 belong to Ihe New Zealand Shipping Company. 



The only important differences in the vessels consist in 

 an increase in length of the Otaki of 4 feet 6 inches to 

 make up for the loss in cargo capacity due to three shaft 

 tunnels instead of two, and also the modified design of 

 the stern and stern post in the same sliip. The boiler 

 installations in the three vessels are identical. The engines 

 of the Otaki consist of two sets of ordinary triple- 

 expansion reciprocating engines driving wing propellers, 

 and a low-pressure turbine driving a central propeller. In 

 ordinary ahead working the reciprocating engines exhaust 

 into the turbine, and change valves are fitted so that the 

 reciprocating engines can also e.xhaust direct to the con- 

 densers. 



.'\t the trials on the measured mile at Skelmorlie the 

 Orari attained a mean speed of 14-6 knots ; the Otaki, 

 under the same conditions, attained a mean speed of 

 more than 15 knots for a total water consumption per 

 hour of 6 per cent, less than that of the Orari. The total 

 water consumption per hour in the Otaki at 14-6 knots 

 was 17 per cent, less than in the Orari at the same speed. 



On the run from the Clyde to Liverpool, with the vessel 

 partly loaded, on November 21 and 22. iqoS, at about 

 half power, the coal consumption was about 1387 lb. per 

 horse-power per hour for all purposes. Scotch coal was 

 used, having a heating value of about 7500 centigrade 

 units. 



.'\s regards the performance of the Otaki on service, 

 the coal consumption on the voyage from Liverpool to 

 Teneriffe was 11 per cent, less than the mean for the 

 sister vessels Orari and Opawa under similar conditions 

 and at practically the same speed. For the round voyage, 

 at the same speed, the coal consumption of the Otaki is 

 about S per cent, less than that of her sister ships. The 

 engines of the Otaki made a non-stop run from Teneriffe 

 to New Zealand, a distance of ii,66q miles as logged, 

 which is probably the longest continuous run yet made by 

 a marine turbine. The turbine worked perfectly satis- 

 f.-ictorilv throua^hout the whole round voyage. 



The "New Zealand Shipping Company is to be con- 

 gratulated in allowing this exoeriment to be made, and 

 also for its courtesv in rendering available the verv full 

 information contained in the paper regarding the perform- 

 ances of their vessels. 



PAPERS ON REPTILES AND FISHES. 



A NEW species of leathery, or leather-back, turtle from 

 -^ the Miocene of Maryland is described by Mr._ W. 

 Palmer in No. i66q of the Proceedings of the U.S. National 

 Museum under the name of Psephophorus calvertetisis, this 

 being the first representative of the genus, which was 

 previously known from the Tertiaries of Europe and Egypt, 

 hitherto recorded from .American deposits. It is, however, 

 pointed out that certain dermal armour from the Zeuglo- 

 dont Limestone of North .America, figured by Mtiller in his 

 work on Zeuglodon, probably belongs to the same genus. 



In No. !6Si of the same publication Dr. L. Stejnege"- 

 gives the name Mesopeltis longifrenis to a snake from 



