OcTOIiER 22, 1896] 



NA TURE 



609 



iiieasiireil is attached to the stage of the microscope, the tra- 

 versing; slide of which is provided with a vernier scale, while a 

 vernier cross-hair in the eye-piece forms the index of the in- 

 sirunient. When the micrciscope has been adjusted for clear 

 focus, the screw is traversed across the field until the cross-hair 

 intersects the thread of the screw at the desired point. The 

 traversinj; screw of the slide is then turned until the correspond- 

 ing point of the next thre,ad is intersected by the cross-hair, and 

 the reading of the vernier on the scale gives the measurement of 

 the pitch with great accuracy. 



The Committee decided that gauges for ordinary workshop 

 use would Ik; best tested, as regards pitch and form of thread, 

 by a template or "comb," the accuracy of which would be 

 verified by the photographic method. Kxternal dimensions could 

 l)e obtained by micrometer gauge, and the internal diameter, or 

 core, by a gauge suggested by Mr. A. Stroh, a member of the 

 Committee, the details of which have yet to be worked out. The 

 Committee failed lo discover any very trustworthy method of test- 

 ing a female standard gauge. Naturally a mathematically accurate 

 male gauge cannot be screwed into a mathematically accurate 

 female gauge of like dimensions, but the variation should not ex- 

 ceed a " good fit." A table prepired by I'rof. Le Neve Fo.ster, 

 dealing with this subject, was added as an appendix. The details 

 given refer to works managers' gauges. Those used by the 

 workman or foreman need not possess the mathematical accuracy 

 of the standard gauges. For full details of this useful report, 

 we must refer our readers to the published Proicedings of the 

 A.ssociation, where it will be found printed together with the 

 illustrations necessary for its full comprehension. 



.\ long paper, by Mr. W. H. Prcece, on "The Tests of 

 <ilow-Lamps," followed. It comprised the results of a very 

 large number of tests, the details being given in diagrams 

 handed round at the meeting. It would be impo.ssible here to 

 give even a summary of the results of tests, for the lamps tried 

 were supplied by a number of makers, and varied according to 

 the numerous conditions of trial. Some of the cheaper lamps 

 gave results not at all in accordance with what would be expected 

 from them if the statements of the makers were to be taken as 

 guides. The experiments tended to prove that in continuous 

 lighting for 1000 hours the candle-power fell about 30 per 

 cent., and the watts per candle-power rose about 28 per cent. 

 Lani]'s for in.stallation work of about 3? watts per candle-power, 

 burning from seven to nine hours per day, behave, as regards 

 life and efficiency, about the same as when giving continuous 

 illumination ; but high efficiency lamps deteriorate more quickly. 

 Good 100 lo 105 volt i6-candle-power lamps, taking 3} volts per 

 candle, should stand a gradual increase of pressure of direct 

 current up to 225 or 280 volts in 3i minutes before the filament 

 breaks. When the pressure is regularly raised in 2A minutes to 

 170 volts, and afterwards re-tested at ordinary voltage, the 

 candle-power should not be less than I4'4, nor higher than I7'6, 

 while the waits per candle should not exceed 4. The author 

 also suggested in his paper a quick and ready way of satisfactorily 

 judging the quality of lamps. To obtain this end the voltage of 

 several lamps was gradually run up for each lamp singly at a 

 uniform rate until the filaments broke. At the moment of 

 rupture the voltage, current, and time of running up were noted. 

 Before increasing the normal voltage the current was measured 

 and the resistance calculateil. The average breaking voltage of 

 the filaments was found to be 230, and the lime of running up 

 was 3J to 4J minutes. Mr. Preece also gave a standard 

 specification for glow-lamps which he had drawn up for use in 

 the l'o.st Office. 



Prof. Ayrton, in the discussion on the paper, said that it was 

 to be expected, as noticed by the author, that lamjis which gave 

 at first less than their nominal candle-power would last longer, 

 as they were worked at a lower pressure. He pointed out that 

 certain figures given by the author as to the cost of illumination 

 by glow-lamps showed electricity to be dearer than gas burnt in 

 an .\rgand burner, and very largely in excess of gas burnt by the 

 Welsbach system. It had been noted that the illuminating 

 power had gone up in certain glow-lamps, though the voltage 

 remained constant. That was an interesting point, and one 

 ditiicult to account for. It had been thought that the improve- 

 ment was due lo improved vacuum, but this was hardly to be 

 believed, and he suggested it might ari.se from improvement of 

 the filament during use. Prof. Fleming referred to the unsatisfac- 

 tory nature of the standard candle, and also to the importance of 

 personal error in photometric investigation. Mr. Swan approved 

 of the short test .suggested by the author, and pointed out that 



the length of life of a lamp depended upon constancy of pres- 

 sure, a thing often much to be desired in central stations. Mr. 

 Preece, in replying, said that though gas might be cheaper per 

 hour than electricity, yet the ease with which the latter was 

 turned on and oft' led to less light being wasted, and therefore 

 an equality of cost was ])roduced. If, however, local atuhorities 

 would use electricity for tram propulsion, the cost of electric 

 light per hour would be brought greatly below that of gas, in 

 consequence of equalisation of the load factor. 



A paper by Mr. S. B. Colterell, on the " Liverpool Overhead 

 Railway, " w.is next read, in which the author described the en- 

 gineering and other details of this construction. Mr. E. W. 

 Anderson also read a paper on "Electric Cranes," the author 

 expressing opinions favourable to the application of electric 

 jKiwer for lifting heavy weights. Papers on " Hy.steresis," by 

 Prof. Fleming, and on "Street Lighting," by Mr. Walker, 

 were also read. 



The Section had a long sitting on the Tuesday of the meeting, 

 but some of the papers were not of great importance. The first 

 taken was by Captain Jaques, of New Vork, and was on 

 " .Armour and Ordnance.' It was devoted largely to showing 

 the great superiority of the United States over the rest of the 

 world in the field. A spherical balanced valve was described by 

 its inventor, Mr. J. Casey. It is an engineer's fitting involving 

 an application of known principle. Prof. Hele-Shaw next 

 gave an interesting description of certain instructional apparatus 

 used in the Walker Engineering Laboratory, including Froude's 

 dynamometer break, the speaker giving an excellent popular 

 description of this ingenious appliance. A good discussion on 

 the subject of technical education followed, in which, among 

 others. Profs. Perry, Beare, Schrbter (of Munich), Ritter (of 

 Zurich), Merrivale, and Hele-Shaw took part. The opinion was 

 expressed that the course of instruction proposed for the estab- 

 lishments known as Polytechnics, which have been so plentihiUy 

 started in this country of late, is too ambitious, and the apparatus 

 so complicated that evening students have not either time or 

 ability to take advantage of it. Papers on "Colour Printing," 

 by Mr. T. Cond, and on " Expanded Metal," a species of net- 

 wurk made by slitting metallic sheets, were also read. The last 

 sitting of the meeting was held on Wednesday, September 23. 

 A paper by Mr. J. Bell described a system of wreck-raising, 

 which the author and others had worked out. Lifting pontoons 

 are employed in the ordinary way, but in place of the rise of 

 tide lieing used to raise the wreck from the bottom, winches are 

 .adopted. The details of construction were illustrated by 

 models. Finally a lecture on " Motor Carriages," by Mr. 

 .Sennett, was given. It was of an entirely popular character. 



This brought the proceedings in Section G to a close. 



ANTHROPOLOGY AT THE BRITISH 

 ASSOCIA TION. 

 A FTER the President's Address (if. N.'kTiiRE, October i, 

 -^ p. 527), the remainder of Monday was devoted to papers 

 dealing with Prehistoric Archa'ology. Mr. Seton Karr exhibited 

 specimens and photographs of the palaeolithic implements which 

 he h.ad collected in .Somaliland ; these form an interesting link 

 in the series of finds extending from India to Britain. It is well 

 known that ordinary paUtolithic implements of the river-gravel 

 type .are wanting in Ireland ; but Mr. W. J. Knowles contends 

 that the older flint implements he has found in the north-east of 

 Ireland belong to this epoch, and that .some bear stria; which 

 "have been pronounced to be glacial." A discussion arose in 

 the afternoon, in connection with some photographs of dolmens 

 in Brittany exhibited by Prof Heidman, as to the age of such 

 structures. Prof. Boyd Dawkins mainiained that they belonged 

 til the Bronze Age, while Dr. Montelius, Dr. (larson, and others 

 recognise that they are essentially Neolithic. 



The proceedings on Friday commenced with speeches by the 

 President, Sir William Turner, Prof. A. Macalister, and 

 Mr. Brabrook, in commemoration of the centenary of the 

 birth of Prof. .^. Retzius, who was the originator of .some 

 of the modern methods of craniology, and who did a great 

 deal lo stimulate anthropological science in Scandinavia. Mr. 

 A. W. Moore and Dr. J. Beddoe read a joint communication 

 on the physical anthropology of the Isle of Man as analysed 

 from the " Description Book of the Royal Manx Fencibles,'' 

 in which are contained particulars of 1 1 12 Manxmen en- 

 rolled between 1803 and 1810. Speaking roughly, there are 



NO. 1408, \OL. 54] 



