December 1, 1896.] 



KNOWLEDGE. 



277 



variety" of T. lineatum, I would advise Lim to send it 

 to the Eev. 0. Pickard-Cambridge, Bloxworth Rectory, 

 Wareham. 



From the account of the shooting lines, etc., I should 

 imagine Elmsett to be a venj wonderful place for spiders, 

 though I much doubt if anyone could rise from his seat, 

 go to the window, etc., without creating enough draught 

 to float a spider's thread. 



The second " marvellous illustration " loses all its charm 

 from the fact that there are so many draughts about a 

 dinner party, which might account for the strange lines 

 being seen. ^^ A Sptoeeman. 



EUNES AND O&nAMS. 

 To the Editors of Knowledge, 

 Sirs, — In the October Number of Knowledge, page 233, 

 I notice that " runes " were found on the Potomac Eiver. 

 I happened to be in Washington when this hoax was 

 started in a local paper, probably as an advertisement for 

 a storekeeper in whose window the copy of the alleged 

 inscription was exhibited. The thing was so palpably 

 absurd that few were deceived. The translation, no doubt, 

 was perfect. This happened nearly thirty years ago, and 

 is a specimen of the survival of the unfittest. 



Washington, D.C., U.S.A. Chas. A. Bchott. 



October 18th, 1896. 



On page 251 of Kj.owledqe for November, Prof. Auvvers' name 

 was. by a priater's error, spelt " Amvers." 



Koticc s of IS oofeg. 



Applied Magnetism. An Introduction t<i the Denii/n of 

 Electmnifiiinetic Apparatus. By J. A. Kingdon, B.A. 

 (Alabaster, Gatehouse, & Co.) Illustrated. 7s. 6d. In 

 mathematical works it has been usual to discuss the 

 phenomena and laws of magnetism from the point of 

 view of a unit magnetic pole. But a magnet has 

 two poles, and the result of building upon the idea 

 of the work done by or upon isolated poles is a mass 

 of theory of little practical value. A simpler and much 

 more satisfactory way to treat the subject is to con- 

 sider a magnet as a conductor of a flow or flux of mag- 

 netism, and thus analogous to an electric conductor. The 

 force or agency — it may be an electric current or a per- 

 manent magnet — which sets up magnetic flux is called the 

 magnetomotive force, and is similar to electromotive force, 

 while the magnetic current or total magnetic flux is found by 

 dividing the magnetomotive force by the magnetic resistance, 

 or reluctance, as it is called. The work before us is dis- 

 tinguished by the fact that this magnetic resistance method 

 of dealing with magnetism is followed. The result is a 

 clear and simple description of modern ideas of magnetism 

 applied to the design of dynamos and other electromagnetic 

 apparatus. In sixteen chapters the author deals with the 

 general principles of magnetism, electromagnetic units, 

 magnetomotive force, magnetic traction, generation of 

 electromotive force, qualitative magnetism, the alternator, 

 the dynamo, magnets and magnetic leakage, commutators 

 and collectors, hysteresis, alternating magnetic flux, electro- 

 motors, polyphase currents and rotary fields, and magnetic 

 measurements. 



The nomenclature of magnetic imits is still in a some- 

 what undefined condition, but the diflerence of opinion 

 that exists as to the names to bo yiven to practical 

 magnetic units does not, of coui-se, aft'ect the character of 

 Mr. Kingdon's work, which is excellent in text and 

 arrangement, and will serve to give students of electrical 

 engineering exact ideas on the science of magnetism 

 without the use of higher mathematics. 



The Wonders of Modern Mechanism. By C. H. Cochrane. 

 (Illinois : Lippincott.) The author has given in this book 

 wonderfully clear and simple explanations of a great 

 many inventions and mechanical appliances. It is 

 essentially a popular account of the wonders of modem 

 mechanism, and the author has been eminently successful 

 in imparting a great deal of knowledge in simple terms. 

 In order to show the scope of the book, we may mention 

 that it treats of the following, amongst a large number of 

 subjects: — Bridges, electricity, ships, horseless vehicles, 

 mining and many other kinds of machinery, printing, and 

 other industries. It will be read with the greatest interest 

 by everyone, and will prove useful as a book of reference, 

 although a complete index would have made it much more 

 valuable in this respect. 



BOOKS EECEIVED. 



Worms. Rotifers, and Toli/zoa. By F. W. CramblC; M.Sc. : Miss 

 L. Sheldon : A. E. Shipley, M.A. ; and Others. (MaomiUan.) 

 Illustrated. Its. 



Prehi'^loric Man and Beast. Br Kev. H N. Hutchinson, B.A., 

 F.G.S. (Smith. Elder.) Illustrated. lOs. 6d. 



Bahif and Instinct. By C. Lloyd Morgan, F.G.S. (Arnold.) 

 Illustrat«d. 16s. 



T/ie Clue to the Ages. By E. J. Page. (Baptist Tract and Book 

 Society.) 



Auiotjiograpliy of Sir George 3. Airg. K.C.S.. M.A., LL.D.. F.R.S. 

 Edited by Wilfrid Airy, B.A. (Cambridge University Press ) 12s. 



Life in Ponds and Sljvams. By W. Furncaux, F.R.Gr.S. 

 (Longmans.) Illustrated. 12s. 6d. 



Sound the Tenr. By Prof. L. C. Miall, F.K.S. (ilacmillan.) 

 Illu9trat«d. OS. 



■Tospph Thomson, African Explorer, By his Brother. (Sampson 

 Low.) Illustrated. 



Alternating Currents. By D. C. and J. P. Jackson. (MaomiUan.) 

 Illustrated. 14s. 



Higher Mathematics. By Mansfield ilerrinian and R. S. AVoodward. 

 (New York: Wiley, London : Chapman k Hall.) 21s. 



The Gases of the Atmosphere. By William Bamsav, F.R.S. 

 (MaomiUan.) Illustratod. 6s. 



Structural Bolani/. Part IT.—Floioerless Flints. By D. H. 

 Scott, M.A., F.R.S. (A. & C. Black.) Illustrated. 8s. 6d. 



The Elements of Phgsics. Vol. IT. — Klecfricitg and Magnetism. 

 By E. L. Nichols and W. S. Franklin. (MaomilUn.) Illustratod. tjs. 

 'Fuel and Sefractorg Materials. By .V. H. Soxton, F.I.C. 

 (Blackie.) Illustrated, as. 



Bell's Beader's Shakr.ipeare. Jul. II. — The Tragedies. (Hoddor.) 

 3.S. (id. 



The Model Locomofire Engineer. By Miohucl Reynolds. New 

 Edition. (Crosby Lockn-ood.) Illustrated. 3s. 6d. 



EIrmenlarg Decoration. ByJ. W. Facey. Third Edition. (Crosby 

 Lockwood.) Illustratod. 2s. 



Induction Coils and Coil-Making. By F. C. .\llsop. (Spcn.) 

 Illustrated. 



Prolileins of Blologg. By Cleorgo Saudoman, M A. (S«-aa 

 Sonneusohoiu ) 



The Literature of Music. By J. E. Mattliow. (Elliot Slock.) 



A Xeic Cour.Kr of Experimental Chemistry. By J. Castoll-Evans, 

 F.I.C. (Thomas Murby.) 2s. Gd. 



Phgsiographg for Beginners. By .V. T. Simmons, B.Sc. (Mac- 

 uiillan.) Illustrated. 2s. 6d. 



Bri/ish Patent Law. By H. lla's. (Whittingham.) Is 4d. 



Phgsics Note Boot, with Spaces for the Pupil's Drairiugs of 

 Experiments. (Macmillan.) 2s. 6d. 



SHORT NOTICES. 



The Iteporl of the Citg and (luil Is of LondoH In^tiliitefor tSPri.li, 

 In this report of the work of the London Institute on behalf of " the 

 advancement of technical education," one cannot but fool ]utine<lthat 

 the artizans fail to realize the bonelit« provided for thorn by this 

 department. We find that only twenty-nine thousand four hundred 

 and ninety-four students atteuded these classes hist year, out of the 

 nuUlitudes of young workers who require teohnii'al training. A 

 second dilliculty is oxperioncod in finding competent teachers for those 

 trade classes, and it seems to be generally admitted that the Iwst 

 instruotors have yet to ho found, as witness many of tlic reports of 

 the examiiu'rs at the cud of tliis report. 



William Wesley A Sons send us their useful eatiloguc (No. 126, 

 1890) on invertebrate zooIog\'. All those who desire to study tho 



