586 



SCIENTIFIC NEWS. 



[June 22, iJ 



exferiment. A saturated solution of salt should have 

 been prepared. This is made by shaking in a bottle an 

 excess of salt with the water. As salt is more soluble in 

 cold than in hot water, the operation must be done at 

 ordinary temperatures. As colouring matter a little 

 ferric salt with sulphocyanide of ammonium may be 

 added, or any ink that is soluble in water may be used. 



The solution is now poured into the plate so as to rise 

 above the edge of the funnel and keep it immersed. It 

 at once rises through the salt, colouring it as it ascends. 

 As fast as it rises, it of course leaves the plate. Hence 

 the experimenter must make repeated additions cf solu- 

 tion. As the fluid rises it drives out the air before it. 

 'I his would escape from the mouth of the funnel. But 

 the balloon which has been placed there intercepts its 

 escape. The air enters and rapidly inflates it. The 

 pressure thus produced is slight. It cannot do more 

 than just fill the balloon. It cannot distend it. But by 

 having the balloon well stretched, its inflation can be 

 made quite conspicuous. 



If, by settling, the salt has left any space between 

 itself and the wal's of the funnel, the possible pressure, 

 slight at the best, will be greatly diminished. If the 

 balloon exerts the least back pressure, air will bubble 

 out of the weak spots around the rim of the funnel. 



By substituting for the salt a cone of porous clay, a 

 more permanent apparatus could be readily constructed. 

 — Scientific American. 



NEW METHOD OF NATURE PRINTING. 



A FEW years ago, Mr. Horace M. Engle devised a 

 method, which he has recently pubHshed in the 

 Botanical Gazette, of taking very beautiful leaf prints. 



The requisites for the work are : i. A small ink roller, 

 such as printers use for inking type. 2. A quantity of 

 green printer's ink. 3. A pane of stout window glass 

 (the larger the better), fastened securely to an evenly 

 planed board twice the size of the glass. A small 

 quantity of the ink is put on the glass and spread with a 

 knife, after which it is distributed evenly by going over 

 in all directions witli the ink roller. When this has been 

 carefully done, the leaf to be copied is laid on a piece of 

 waste paper, and inked by applying the roller once or 

 twice with moderate pressure. This leaves a film of ink 

 on the veins and net-work of the leaf, and by placing it 

 on a piece of blank paper and applying considerable 

 pressure for a few moments, the work is done, and when 

 the leaf is lifted from the paper, the impress remains 

 with all its delicate tracery, faithful in colour and out- 

 line to the original. 



Tj get the best results, however, several points must 

 be carefully noted. The ink, as sold, is invariably too 

 thi:k for this purprse, and should be thinned by adding 

 several drops of balsam copaiba to as much ink as may 

 b ; taken on a salt spoon. 



Much depends on the proper consistency of the ink. 

 In inking, the leaf is apt to curl on the roller, but it 

 should part readily from it. In case it sticks tightly, the 

 ink is too thick. Take care that the ink is evenly distri- 

 bute! on the glass and roller, as it is essential that 

 each part of the leaf receives an equal coating of ink. If 

 the le if is large, ink it part by part, keeping the roller 

 supplied frequently. A roller three inches long will 

 arsw-r for all small leaves and branches of plants. If 

 ih< leaf is finely veined, the lower surface makes the 

 be't r print, but if the veins are coarse and large, the 



upper surface may be used. If the specimen be fleshy 

 or brittle, allow it to wilt until it becomes more pliable, 

 or, if necessary, it may be pressed and dried first. In 

 most cases the best copy is obtained after taking one or 

 two impressions, as the leaf takes the ink better after 

 several applications. A good quality of unsized paper 

 that is made slightly damp by putting in a cellar several 

 hours before using is best for general work, but in other 

 cases well-sized paper will take a copy that will allow an 

 impression to bear inspection side by side with a good 

 lithograph. A copying press will be found very valuable 

 in making the impression, especially if the leaf is at all 

 coriaceous. If it be soft, it should be covered with .t 

 few thicknesses of newspaper. If it be irregular in 

 thickness, paper may he laid over the thin parts, so that 

 equal pressure is received. This is necessary with all 

 leaves that have thick stems. If the leaf or branch be 

 very irregular or delicate, or in the absence of a press 

 of any kind, the specimen may be covered with several 

 layers of paper, and held in place with one hand while 

 the pressure is applied with the thumb or palm of the 

 other hand. 



For illustrating monographs and similar papers where 

 the number is too limited to warrant an expensive litho- 

 graph, for identifying a rare specimen, or as an 

 adjunct to an herbarium combining portability, unal- 

 terability, and beauty withal, the method seems par- 

 ticularly fitted. But aside from this, others may find a 

 delightful and instructive recreation in taking prints of 

 the entire flora of an old farm, the trees of a certain 

 grove, the native animals of a county, the ferns of a 

 state, or any other special field that seems most inviting. 

 Such copies may be taken in a blank book suited to the 

 purpose, or better, taken on single sheets of uniform 

 size, as in this way imperfect copies may be thrown out, 

 and when the work is completed, named, classified, and 

 bound, thus making a volume of real value. 

 — ■^-;»»^<^5<^-^— 



Magnesium. — The following experiments were made for the 

 aluminum and magnesium manufactory in Bremen, at the 

 mechanical experimental station in Charlottenburg. Tensile 

 strength, limit of breaking, 23.2 kilos per i sq. mm., specific 

 resistance to compression 27.2 kilos per i sq. mm., bending 

 strength 17.4 kilos. In comparison with other metals, the 

 strength of magnesium is relatively very considerable. The 

 breaking coefficient for tensile strain per square millimetre is : 



Specific 

 Kilos. Giavity. 



Magnesium 23.2 1.75 



Aluminum 20.5 2.67 



Brass _ 12.5 7-8-95 



Bronze 23.0 8-9 



Rod iron 38.0 7.6-7.8 



Delta metal, poured in sand 34-36 8 6 



Delta metal, rolled baid 53.0 — 



Since the rolling of magnesium does not offer the slightest 

 difficulty, even in such complicated forms as T I U, or as 

 angles, round or four-cornered rods, plates or sheets of 

 o. I mm. thickness, and as pure magnesium is sufficiently 

 resistant to atmospheric influences and can be polished and 

 easily cleaned, it lends itself on account of its lightness and 

 relative strength to the construction of apparatus, etc., 

 required to be made of metal and also to be light, as, for 

 instance, nautical, physical, and astronomical instruments. 

 The working of magnesium requires heat. At a temperature 

 of 450° C. it can be rolled, pressed, worked, and brought 

 into complicated forms. Screws and threads can be made of 

 magnesium, and these are considerably sharper and more 

 exact than those from aluminum. Owing to its cheapness, 

 magnesium can also be used in the manufacture of a variety 

 of useful articles. Experiments in this direction are now 

 being made, — Joiir. Soc. Chem. hidnstry. 



