128 



SCIENTIFIC NEW^S. 



[April 6, 1888. 



he is unfamiliar. Having regard, however, to the views 

 recently expressed by the author in a paper contri- 

 buted to Science-Gossip, we expected to find the name 

 Lehtnannia 'marginata substituted for Liniax (Eiilimax) 

 arborutn. Notwithstanding its slight deficiencies, the 

 hand-book with which Dr. Williams has furnished us 

 will be found of great use, and most conchologists, 

 especially those who reside far away from the great 

 public libraries, unless they wish to part company with 

 their fellow-workers, will doubtless avail themselves of 

 its help during the years which must elapse before the 

 comprehensive and exhaustive monograph upon which 

 Messrs. Taylor and Roebuck, of Leeds, have for some 

 years past been engaged, can be expected. 



Boys' Games. A Recreation Handbook for Teachers and 



Scholars. Edited by E. D. Bourne. Price 6d. 

 GirH Games. A Recreation Handbook for Teachers and 

 Scholars. Edited by E. D. Bourne. Price 6d. 

 London : Griffith, Farran, Okeden and Welsh. 

 These two little books are both calculated to be very 

 useful. The introduction to both contains some 

 matter which may well call for serious reflection. The 

 author admits some at least of the main points in the 

 necessary indictment of the " tendencies of the age." 

 He says, " The wear and tear of life as regards its 

 mental, jf not its bodily, condition, the strain of nerve 

 and the expenditure of brain power have increased with 

 the pressure of population and competition " — a pressure, 

 surely, which in many respects has been needlessly and 

 wantonly created ! Again, " it is our duty to lessen, as 

 far as can be, the fresh difficulties that modern progress (!) 

 has put in the way of our young people's proper 

 growth." It may well be asked whether anything which 

 puts difficulties in the way of the vigorous development 

 of the people deserves to be called "progress " save in an 

 ironical sense. 



So long as Governments, irrespective ot party, are 

 encouraging the present systems of education, what the 

 individual — be he teacher or author — can effect will be 

 little. 



Still more urgent, because less regarded, is the necessity 

 of improved physical training for girls, a matter which has 

 been most fearfully neglected alike by mothers and by 

 the heads of schools. The abuses of language have often 

 been fraught with grave mischief, but perhaps the 

 saddest instance of this kind on record is the common 

 use of " delicacy " as a synonym for debility and the 

 kindred employment of such expressions as " rude 

 health." 



The Journal of the Franklin Institute. Series iii. Vol. 

 XCV. No. I, January 18SS, and No. 2, February, 

 1888. 

 By far the bulk of the matter contained in these 

 numbers is of too strictly technical a character to interest 

 the non-professional reader. We notice, however, a 

 paper on the "Japanese Magic Mirror," by Mr. F. E. Ives. He 

 observes that these mirrors are slighly convex, and when 

 they are placed several feet from the eye objects reflected 

 in them appear irregularly distorted. He concludes that 

 to reproduce the figures at the back of the mirror, it is 

 sufficient to have the surface slightly less convex on these 

 parts. In proof it is mentioned that if the mirror is 

 flattened by pressure, the figures vanish from the re- 

 flection. The first of these magical mirrors was probably 

 not produced intentionally. 



Another noteworthy paper by the same writer is on 

 the "ether ox j'gen lime-light," which is now coming into 

 use instead of the oxy-hydrogen for exhibiting dissolving 

 views, etc. Owing to recent improvements it is free 

 from noise, flickering and danger. It is worked not 

 with ordinary ethylic ether, but with petroleum ether, 

 which is cheaper, evaporates at a lower temperature, and 

 contains neither alcohol nor water. 



■ — -K^i^"^**?-* 



RAPID METHODS OF PREPARING 

 LANTERN-SLIDES. 



LANTERN-SLIDES are often wanted in a great hurry, 

 when photography is of course out of the question. 

 The following methods may be substituted with advan- 

 tage where nothing but line work is required : — 



(i) Rub a warm glass plate with a paraffin candle, 

 wipe it nearly clean, and smoke with a camphor flame 

 till a uniform coating of dark brown is obtained. Upon 

 this ground figures may be drawn with a needle. 



(2) Smoke a clean plate, and, after etching, fix the film 

 by the vapour of heated alcohol. The plate may then be 

 secured with photographic varnish. 



(3) Coat a plate with thin gelatine solution (warm). 

 When dry, pen-and-ink drawings may be made on the 

 surface so prepared. Clean, dry slides can be stored for 

 future use. 



(4) Stain a good photographic varnish with some 

 aniline colour soluble in alcohol. Ruby, purple, and 

 blue are good colours to use. Mix a little mastic with 

 the varnish to get a suitable texture when dry. The exact 

 proportion must be determined by trial for each kind ot 

 varnish. If too much mastic is used, the film becomes 

 " matt," and chips easily when dry. Varnish a number 

 of plates with this solution, just as the photographer 

 varnishes negatives. The plates are dry in a very few 

 minutes, and ready for use. 



A retouching-desk is necessary for careful work. The 

 needles for etching should be mounted in sticks, and 

 care must be taken that they are not so long as to be 

 flexible. 



Process 4 is the best for ordinary use. Any number 

 of shdes can be varnished beforehand, and kept in a box 

 for emergencies. The tinted ground has a very pleasant 

 effect on the screen. Lastly, the slides can be put into 

 the lantern without cover-glass, if time presses. Some 

 lecturers, who have the lantern always at hand, use such 

 slides for rapid, almost extemporaneous, diagrams, for 

 tables of figures, and even for examination papers. A 

 large class can copy down any written matter from such 

 slides with great ease. When done with, the slides are 

 readily cleaned. Very artistic and beautiful work can be 

 turned out by a good draughtsman on the delightfully 

 free surface of the varnished plate. 



Violet Copying Ink. — Dissolve 40 parts of extract ol 

 logwood, 5 of oxalic-acid, and 30 parts o) sulphate of alumi- 

 nium, without heat, in 800 parts of distilled water and 10 

 parts of glycerine ; let it stand twenty-four hours ; then add 

 a solution of 5 parts of bichromate of potassium in 100 parts 

 of distilled water, and again set aside for twenty-four hours. 

 Now raise the mixture once to boiling in a bright copper 

 boiler, mix with it while hot 50 parts of wood vinegar, and, 

 when cold, put into bottles. After a fortnight decant from 

 the sediment. In thin layers, this ink is reddish- violet, it 

 writes dark violet, and furnishes bluish violet copies. 



