JUNt 25, 1903] 



NATURE 



87 



leaving the latter task to the speakers in the discussion ; of 

 these there were no less than twenty-five. They included 

 Sir W. H. White, Prof Kennedy, Colonel Crompton, Cap- 

 tain Sankey, Profs. Ayrton, Burstall and Capper, the Hon. 

 R. C. Parsons, and Messrs. D. Drummond, A. K. Yarrow, 

 E. B. Ellington, Bertram Hopkinson and Mark Robinson. 

 Most diverse opinions were expressed by the various 

 speakers, but it may be said generally that some system in 

 which a college course would alternate with practical ex- 

 perience, in periods of greater or less duration, received 

 acceptation. Sir William White, in closing the discussion, 

 gave a promise that the matter would be considered by the 

 council of. the Institution of Civil Engineers, which would 

 take into consideration what had been said in the section, 

 as well as the proceedings before the Institution of 

 Mechanical Engineers and the Institution of Naval Archi- 

 tects, both of which had had presented to them papers on 

 this subject by Prof. W. E. Dalby, who recently made a 

 tour in .America and on the Continent to study this question. 



Mining and Metallurgy. 



Seven papers were read in this section. The first taken 

 was by Sir Thomas Wrightson, Bart., M.P., and Mr. John 

 Morison, the subject being " Notes on Percussive Coal 

 Cutters." Details of the machinery were given, the authors 

 arriving at the conclusion that in America machine coal- 

 cutting had been successful, but in this country, up to the 

 present, almost the opposite experience had been the result 

 of the adoption of machinery, the economy, except in special 

 cases, being doubtful. 



" Recent Improvements in Gold-mining Machinery on the 

 Rand," by Mr. A. E. T. Lees, followed. He dealt with 

 the labour difficulty and its effect on the introduction of 

 labour-saving devices. Considerable progress has recently 

 been made in surface works, as well as certain improve- 

 ments in mining machinery generally. 



Mr. J. H. Harrison read a paper on " Equalising the 

 Temperature of the Blast for Blast-furnaces, and its Effect 

 on the Melting Zone." He gave particulars of the practice 

 followed in America for preventing " scaffolds." 



" Notes on Steam-driven and Gas-driven Blowing 

 Engines " were contributed by Mr. Tom Westgarth, who 

 had no hesitation in saying that the gas engine generally 

 was more suitable for blast-furnace work, provided always 

 that the gas saved by the use of the gas engine could be 

 readily employed. 



The remaining three papers read in this section were : — 

 "The Continuous Method of Open-hearth Steel-making," 

 by Mr. B. Talbot; "Alloys of Iron, Nickel and Man- 

 ganese," by Mr. R. A. Hadfield ; and "The Dangerous 

 Crystallisation of Mild Steel and Wrought Iron," by Prof. 

 J. O. Arnold. 



Shipbuilding. 



Section v. had five papers before it. The first was by 

 Mr. A. F. Yarrow on " The Comparative Merits of Drilling 

 and Punching in Steel for Shipbuilding." The author gave 

 particulars of the British Aciniiralty regulations, which re- 

 quire drilling in place of punching for light vessels. He 

 had found by experience that this was a wise provision, 

 although it had been objected to by some contractors. In 

 the discussion which followed, it was allowed that a drilled 

 hole was better than a punched hole for light vessels, such 

 as torpedo craft. For merchant ships, however, the greater 

 expense of the drilling might be objected to. 



Mr. John List read a paper on " Screw Shafts," pointing 

 out the severe effects set up in them by racing in light 

 vessels. He referred to the growing use of nickel steel for 

 propeller shafts. 



Mr. A. E. Seaton also read a paper on " The Modern 

 Express Steamer for Short Passages," whilst Prof. A. 

 Rateau dealt with " Steam Turbines." Mr. H. H. West 

 contributed a paper on " Harbour Dues and Charges." 



Water-works, Sewerage and Gas-works. 



\ Five papers also were read in this section. The first 



was by Mr. G. T. Beilby on " Smoke Abatement." The 

 author looked forward to the spread of the internal com- 

 bustion engine and electric transmission of power to pro- 

 duce a better state of the atmosphere in large towns. 



NO. 1756, VOL. 68] 



He also considered that the firing of steam-boilers with 

 washed gas would prove advantageous. 



The next paper read was by Dr. S. Rideal, and was on 

 " Coal-gas Standards." The subject is not one that lends 

 itself to compression. The same may be said of Prof. 

 Percy F. Frankland's paper on " The Bacterial Treatment 

 of Water and Sewage." The other papers read in this 

 section were : — " Steam Turbine-driven Centrifugal Pumps 

 for High Lifts," by Mr. C. W. Darley ; and " The Raising 

 of W'ater by Compressed Air," by Mr. Percy Griffith. 



Applications of Electricity. 

 Five papers were read in section vii. The first was on 

 " Wireless Telegraphy," introduced by Mr. E. A. N. 

 Pochin, who gave a review of the principles involved in 

 this subject and of recent developments. Among important 

 facts which have lately been established are : — (i) up to 

 considerable ranges earth-curvature is not a fatal obstacle, 

 but hills may exercise a serious influence ; (2) the ether 

 exhibits what we may provisionally call a variable trans- 

 parency to Hertzian waves, sunlight being an important 

 factor. With regai'd to both these phenomena, it is 

 probable that certain wave-lengths offer special advantages, 

 whilst the second affords a faint clue to the relative share 

 of earth and ether in transmission. Amongst problems, 

 that of isolation is undoubtedly the most important, and in 

 this direction two methods have been employed, which may 

 be termed respectively syntonic and optical methods, both 

 of which were described as regards performance and 

 promise. During the discussion which followed, Mr. 

 Gavey expressed the opinion that syntony in installations 

 of wireless telegraphy of from 60 to 100 miles could be 

 established, and maintained with certainty and regularity ; 

 but for long distances transmission was uncertain, owing 

 to causes which were not apparent. The remaining papers 

 read in this section were on the " Applications of Electricity 

 to Driving Carriages in Towns," by Lieut.-Colonel R. E. B. 

 Crompton, C.B. ; " The Transmission and Distribution by 

 Single-phase Alternating Current," by Mr. E. W. Monk- 

 house; "High-speed Electric Traction on Railways," by 

 J. W. Jacomb-Hood; and "The Position and Protection 

 of the Third Rail on Electric Railways," by Mr. W. E. 

 Langdon. 



liEW CASE OF PROTECTIVE MIMICRY 

 IN A CATERPILLAR. 

 T T is well known that the larvae of many insects, such 

 •^ as those of the case moths, clothes moths, caddis flies, 

 tortoise beetles, and the masked bug, construct for them- 

 selves cases or artificial coverings either for protection or 

 concealment, and a new and somewhat remarkable instance 

 is described by Mr. R. Shelford, the curator of the Sarawak 

 Museum, in the Zoologist for May. We are indebted to 

 the publishers for the accompanying illustration of the 

 caterpillar described. 



On May 16, 1900, a native collector brought in a quantity 

 of a Spiroea-like plant, intended for the food of butterfly- 

 caterpillars. It bore numerous pale green cymose in- 

 florescences which were still in bud, and presently one of 

 the branchlets was noticed to be moving. This proved to 

 be due to the presence of a small Geometer caterpillar (only 

 9 millimetres in length) covered with buds from the in- 

 florescence on which it was feeding. This " bore the follow- 

 ing spine-like processes, a dorsal pair on the 4th segment, 

 a dorso-lateral pair on segments 5, 6 and 7, a lateral 

 pair on the 8th segment, and a short dorsal pair on the 

 nth; there were also some small tubercles in the positions 

 shown in the accompanying sketch." To these spines 

 strings of buds, connected by silk, were fastened in a 

 similar manner, and when the green buds faded, or were 

 removed, they were immediately replaced by fresh ones. 

 " A bud would be shorn off with the mandibles, then held 

 in the'two front pairs of legs, and covered all over with 

 silk issuing from the mouth of the larva ; the larva then 

 tvvisted round the anterior part of the body, and attached 

 with silk the bud to one of the spinous processes, and 

 another bud would then be attached to this, and so on, until 

 a sufficiently long string (generally three or four buds) was 

 made, when operations on another spine would be com- 



