Oct. 20, 1882.J 



♦ KNOWLEDGE 



34; 



you hold it over it. Be careful that the paper is equally 

 black all over, as otherwise the impression will be blotchy. 

 When you have clone this, extinguish your candle and 

 place your prepared paper on the table, black side upper- 

 most. Then take your leaf on which you are going to 

 perform, and, cutting out a piece of black paper of that 

 size, place the leaf upon it ; then, over that, place another 

 sheet of paper, and with your finger rub carefully and 

 evenly o\er the place where the leaf is, taking care not to 

 shift its position. After this, lift off the top paper, and 

 carefully raise your leaf from the blackened paper on to a 

 .■sheet of white note-paper, and, when once you have laid it 

 on, do not move it in the least, or it will smear; then, 

 placing a. clean piece of paper to cover the leaf, again rub 

 well, and quite evenly, over where the leaf lies, for about 

 two minutes ; then remove your paper and leaf and you 

 \\ill find a beautiful impression of the leaf, with all the 

 Acins, even to the most minute, standing out in black. If 

 this is allowed to dry it will not smear in the least, and 

 will always retain its original freshness. 



I do not suppose that my explanation has been very 

 clear, but I have tried to make it as plain as possible. I 

 have seen a very beautiful collection of flowers and leaves 

 done by this method, and when they are arranged in 

 groups or various forms, according to taste, they produce a 

 very pretty effect Some think tinting them with colours 

 also very effective, but that is as your fancy may dictate. 

 J. F. Roberts. 



Electrotyping Telegraph Wires. — The Postal Tele- 

 graph Company of New York have recently acquired an 

 electrotyping establishment in Ansonia, Connecticut, for 

 the purpose of covering the steel w ire they employ with a 

 deposit of copper. The present capacity of the works is 

 sufficient to deposit two tons of copper a day, and extensions 

 are now in progress to treble this amount. When these 

 extensions are completed, !)80-horse power will be employed 

 to drive dynamo machines for supplying the current 

 necessary to cover thirty miles of wire a day, with 500 lb. 

 of copper per mile. 



On Monday a deputation waited upon Mr. Rhaw- 

 Lefevre with reference; to the restricted facilities for 

 entrance to Kew Gardens. The deputation complained 

 that not only were the public excluded from the gardens 

 every day until after 1 o'clock, but the Temperate-house 

 gate, close to the very handsome picture gallery, recently pre- 

 sented by Miss North, was being bricked up, and another 

 entrance made 3.50 yards further down the road towards 

 Richmond. It was pointed out that a large number of 

 houses, ranging in value from .£100 to .£300 per annum, 

 had been erected near th(! Temperate-house gate, and a new 

 road made leading from the railway station to it, in the 

 hope that it would be opened to the pul)lic, but the new 

 gate would be at a spot where there was no population, 

 and would give access to the least interesting part of the 

 gardens. Mr. Shaw-Lefevre informed the deputation that 

 the work was being carried out on the recommendation of 

 Sir Joseph Hooker, the director, who had represented 

 to the Department that it was for the public advantage. 

 It was not desirous to multiply the entrances to the 

 gardens. It was intended not only to lirick up the 

 Temperate-house gate, which had never been open to tlie 

 public, but also to close the entrance now availaljlo for the 

 public near Richmond, opening instead the new gate, which 

 would be very ornamental, between the two. He would 

 consider whether railings could be substituted for bricking- 

 up the Temperate-house gate, so as not to shut out the view 

 from the road. [Why not railings all along 1 — Ed.] 



ilfbi'ttosf. 



MAGNETISM AND ELECTRICITY.* 



ELECTRICAL science and its applications have forced 

 themselves so prominently before the public during 

 the past few years, that it is only natural we should observe 

 a considerable increase in the number of^jublications issued 

 with a view to giving more or less reliable information to 

 those who desire it, or, we may rather say, to cultivate a 

 more extensive taste for it. Amongst the class-books de- 

 signed for the use of those who, having no previous know- 

 ledge of the subject, are anxious to make themselves 

 practically acquainted with its many mysteries, we know 

 of no better than the little work now before us. Dr. 

 Wormell has already gained a well-merited reputation in 

 the world of physical science, which cannot fail to be 

 increa.sed by this, his latest eflbrt. He aptly points out 

 in the preface that " the general purpose of science in 

 education is to cultivate in the student an intelligent 

 attitude of mind in relation to the things and phenomena 

 about him, and to give him ability to describe as well as to 

 examine and use them." The author has, therefore, taken 

 considerable trouble to incorporate an excellent series of 

 instructions in laboratory practice, and has thereby assigned 

 to the work a place by itself. The practice is designed 

 mostly with apparatus of an extremely inexpensive but 

 very efiicient kind, and such as can generally be made by 

 the student. The book is divided into a number of 

 " lectures," each one dealing with a special branch, the 

 lectures on Magnetism being uniformly good, and several 

 of the experiments of a very telling but simple nature. 

 Terrestrial magnetism and its effects upon iron ships, with 

 the means devised for the " correction " of their permanent 

 and temporary magnetisations, are very ably dealt with, and 

 the dangers that would accrue were such corrections neg- 

 lected, are pointed out and illustrated. In the lectures on 

 Electricity, the studious combination of hand and head-work 

 is continued, the experiments growing in interest and im- 

 portance; liut perhaps the best portions of the book are those 

 which deal with measurements and instruments for measur- 

 ing — best, not so much because of their superiority over 

 the other chapters or lectures, but rather because there 

 has hitherto been far too strong a tendency to ignore that 

 branch of the science which entitles it to a place amongst 

 the exact sciences. The lecture on " Capacity and Poten- 

 tial " is an unusually clear and concise exposition of what 

 appears to be to the student one of his greatest difficulties. 

 It makes the important relationship existing between 

 capacity and potential so easily comprehensible, that no 

 further trouble with the subject should be experienced. 

 Careful attention has also been devoted to the explanation 

 of the principles involved in magneto and dynamo-electric 

 machines, as well as telephony and other applications of 

 electricity. 



The work is almost free from errors. There are, liow- 

 ever, a few — possibly printers' — mistakes in the telef»raphic 

 characters, and it is to be regretted than an instrument 

 which has been out of date these last twenty years should 

 be given as an illustration of the Morse telegrajih instru- 

 ment of today. A more serious error has crept in on 

 page 131, wliere, using a Galvanometer of low resistance, it 

 is stated that cells being added in series to increase the 

 electromotive force (E. M. F.), "the current (c) is propor- 

 tional to the E. M. F. producing it, or .... C varies 



• Jl/n<;iu'<ii!iii and Kleclrieitij. An KUmeniary Teil-ltook fir 

 Studeulg. Uy Ui<iiari> Wokmki.i., D.Sc. XI. .\., Head-Master of tlie 

 City of LoiKlon MiiUllo-Class Schools, (bumlon : Thomas Murby.i 



