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KNOWLEDGE c>;- SCIENTIFIC NEWS. 



[April, 1Q05. 



more practical use in the world than he who has devoted the same 

 amount of time to a study of Greek. We commend the book 

 especially to school-masters and others interested in the educa- 

 tion of boys and young men, but none the less do we advise all 

 those who are not well up in these subjects to dip into the 

 book, after which their interest is sure to be aroused, and the 

 work read from cover to cover. 



Remarkable Comets, by W. T. Lynn ; 12th Edition, Revised. 

 (Sampson Lo*-. Marston, and Co., Limited; London, 1905; 

 p.p. 46; price 6d.K Ojr astronomical readers are. no doubt, 

 acquainted with ttiis concise summarj' of the more interesting 

 facts in the history of cometary astronomy, and the present 

 edition, the twelfth, brings the account up to date. .'\s in 

 former editions the author restricts himself to the appearance 

 and reappearance of comets and their periodicities, and only 

 refers in a very brief manner to the relationship between 

 comets and meteor-swarms. The physical characteristics are, 

 as usual, almost neglected, lying outside the scope of the 

 survey. As the book is intended as a handy book of reference 

 to comets which m.iy be considered remarkable, its value would 

 be very much enhanced if, in future editions, a brief biblio- 

 graphy were added at the end. This would most certainly 

 assist those who wish to learn more about comets than that 

 which is contained in these pages, and would be very etficiently 

 done if compiled by the author of this excellent little treatise. 



A Revised System of School Teaching, by Richard Chichester 

 (H. J. Glaisher; is. net). This is a pamphlet describing a 

 new system which might be adopted in schools. The 

 idea is founded upon the fact that " so often a boy, on 

 reaching a high class, being asked a comparatively simple 

 question, answers that he never learnt it " (presumably mean- 

 ing the answer). When such an occurrence is frequent, re- 

 form is certainly needed, but we should have thought it exposed 

 a fault in the detail of teaching rather than in the principle. 

 An idea well worthy of consideration is here suggested, which 

 is that, instead of boys being placed in one " form " or " class " 

 for all subjects, " DiWsions " should be formed for instruction 

 in each particular subject. All schoolmasters should read 

 this pamphlet, which may suggest to them some useful 

 wrinkles. 



A List of English Clubs (or 1905, by E. C. Austen Leigh. 

 M.A. iSpottiswoode and Co.), will often be found of great use, 

 containing as it does not only details of all the London and 

 Provincial Clubs, but also those of English Clubs all over the 

 world, with membership, subscriptions, &c. 



China Decoration and Repair, by Rev. F. C. Lambert (Dawbarn 

 and Ward : 6d.i, h a us«-ful little guide, but contains some 

 very inartistic designs. 



The Children's Book of Moral Lessons, by F. J. Gould (Watts 

 and Co. ; price 6d.). The mor.il instiuction of children is too 

 frequently sadly neglected, and fiiblical History supposed to 

 suffice in this respect. The little work before us is an attempt 

 to impart such moral instruction under the guise of short 

 anecdotes. 



Williams and Norgate's International Book Circular is 

 practically a bibliographical risumc of the world's best literary 

 productions in all branches of science and learning published 

 during the last few weeks, and as such will be found of great 

 value to students of science. 



How to Build a Uthe. By A. W. Burford, A.M.I.C.E. 

 (Dawbarn and Ward), price 6d. net. (cloth is.), forms No. 9 of 

 the series of " Ctility " Practical Handbooks, some of which 

 we have already noticed. To build up a lathe from the raw 

 materials is instructive as well as being a cheap means of 

 obtaining a valuable possession. The instiuctions herein 

 given are very pr.-ictical, and a number of diagrams add to the 

 explanations in the text. 



Lessons In Experimental and Practical Heometry. By H. S. 

 Hall, M.A., aiiJ l'. H. Stevens, M..\. (Macmillan), price is. 6d. 

 It is perhaps quite sound, though not altogether in keeping 

 with practice, " to give to a young pupil clear mental pictures " 

 of geometrical principles. To graphically explain what is 

 meant by lines, planes, angles, and all the other constituents, 

 the consideration of which go to make up geometry, is the 

 object of this little book. The idea is well carried out, and we 

 can confidently recommend this brochure to teachers of 

 elementary Geometry. 



An Improvement in the 

 WimsKurst Machine. 



Bv Charles K. I3e.\il\.\l 



M.ANV years ago the late Mr. Wimshurst established the 

 fact that the electric influence machine which he in- 

 vented will work without the tinfoil sectors if large 

 brushes are used and if the varnish on the plain plates 

 is new. Under such conditions the machine is not 

 only sclf-cxciting, but the sparks arc e\cn longer than 

 when sectors of tinfoil are present. The reason for 

 the increase in spark-length is no doubt the greater 

 immunity from leakage. On the same, or, rather, the 

 converse principle, the increase of the number of 

 sectors diminishes the length of spark on a Wimshurst 

 by increasing the leakage. It is obviously inconvenient 

 to be constantly renewing the varnish on the glass 

 plates, so that the sectorless Wimshurst, though 

 interesting for exhibition as a class-room experiment, 

 is not adapted for practical work. By a simple ex- 

 pedient, however, the efficiency of the machine may be 

 increased and the required immunity from leakage re- 

 duced to a minimum without altogether doing away 

 with the sectors and rendering the self-excitement de- 

 pendent on the condition of the varnish. The way to 

 do this is to make every alternate sector of a semi- 

 conducting substance instead of tinfoil. Thin white 

 card seems to answer best. The cardboard sectors 

 may be larger than the intermediate tinfoil sectors. 

 The only reason why cardboard alone cannot be used 

 is that self-excitement is not assured, espcciall)' in very 

 dry weather. Very narrow sectors of tinfoil between 

 the card sectors will ensure the self-excitement, and as 

 soon as the potential increases, the semi-conducting 

 card acts fully as efficiently as metal, with the ad- 

 vantage that there is considerably less leakage and a 

 longer spark. The arrangement is equally efficient in 

 all sorts of atmospheric conditions, a small vulcanite- 

 disc machine of eight inches diameter responding 

 promptly after being left for some hours near :m open 

 window on a damp, foggy day, and giving at once 

 strong sparks of 2i inches length. The cardboard 

 sectors on each plate of this machine number 16, and a 

 narrow tinfoil strip is placed between each two. The 

 cardboard should be .-ittachcd firmly with strong glue, 

 the corners of the sectors being carefully rounded with 

 scissors before they are fixed to the plate. Woiking 

 the machine at full strain, with the dischargers wide 

 apart, in the dark, its immunity from loss by leakage is 

 at once apparent. 



Acetylene as an Explosive. 



M. fiiTKDRAS has been experimenting in Paris willi 

 acetylene as an explosive. The carbide is granulated 

 and charged in a special form of cartridge, consisting 

 of an iron-cvlinder, in Ihe bottom of which the c.irbide 

 is placed. .Above this is stretched a membrane, and 

 the top is filled with water. .\ rod is .so fixed in the 

 cartridge, that when its end is struck it pierces a hole 

 in the membrane, which lets the water on to the car- 

 bide, and acetylene gas is formed. The charge is fired 

 bv an electric fuse inside the cartridge. 



