210 



HABDWICKE'S SCIENCE-GOSSIP. 



[Sept. 1, 1SG6. 



bubbles, and hardens the balsam. The baking seems 

 to me the principal part in mounting, both for 

 drawing out the bubbles and making the objects 

 durable ; for when the balsam has not been well 

 hardened, they are injured by damp, and always 

 remain sticky, and are easily displaced. In mount- 

 ing dry objects, glass, or wooden cells, secured on 

 with size, are the best for excluding air ; but 

 the size must be allowed to be perfectly dry before 

 the object is put in and the cover on, or a mould is 

 sure to appear. I had a greal deal of trouble with 

 the sticking on of these cells, until I got a cement 

 which I should recommend to all microscopic 

 mounters.—.? 7 . 



Maltwood's Finder. — It has often been a matter 

 of surprise to me that so few microscopists, com- 

 paratively speaking, possess and use Maltwood's 

 Einder ; it is without doubt one of the most useful 

 microscopical appliances with which we are now 

 familiar. 



I am frequently in the receipt of slides of diatoms 

 on which certain special forms are mounted, and 

 attention is often called to frustules by small spots 

 of ink on the cover, or other rough-and-ready modes 

 of indicating localities, all of which modes being 

 very inferior to that of registration according to a 

 uniform finder, such as Maltwood's, which, if pro- 

 perlyused,will iuvariably enable an' observer, or series 

 of observers, to find with ease any registered form. 



The mere registration of a diatom byflgures alone 

 is often not sufficient for immediate re-discovery 

 when high powers, such as £th, -|th, or T \jtb, 

 are used ; but if the registration be carefully con- 

 ducted, and a spot placed on the register, near the 

 locality where the diatom was visible — thus, §£", or 

 •§« — then there is no difficulty in re-observing the 

 object registered, and very much valuable time is 

 saved, which, when a mere rough search is made, is 

 necessarily lost. I have a large series of marine 

 diatoms registered in the manner described, and 

 have not the least difficulty in finding any one of 

 them in an instant. T. P. Barkas. 



PHOTOGRAPHY 



Willis's Aniline Printing Process.— Mr. Vin- 

 cent Brooks, the well-known lithographer, has taken 

 this patent process in hand; and, as a means of 

 superseding manual or mechanical methods of 

 reproducing architectural drawings, plans, &c, it 

 promises to take high ground in public favour. The 

 main advantage of the process is, or rather should 

 be, in its extreme economy where but a few copies 

 are required. In common with other photographic 

 processes, it secures perfect accuracy and rapidi ty 

 of production. A tracing may be used with perfect 

 safety for this purpose, but the paper on which it is 



made should be thin, clear, and colourless, and the 

 drawing made with British, or very black, Indian 

 ink, and the washes given with somewhat more 

 strength than usual. Colours are objectionable, 

 owing to their varied actinic powers. Ordinary 

 sketches on common drawing-paper may be used as 

 negatives ; but, when placed over the prepared 

 surface, the light requires more time to do its work, 

 owing to the increased thickuess of the medium it 

 has to pass through. Where scientific diagrams and 

 drawings are required in small numbers, this pro- 

 cess will be specially advantageous. — /. W. W. 



Woodbury's Photo-relief Printing Process. 

 — Another modification of this valuable and pro- 

 mising process has been made by the patentee, by 

 virtue of which it promises to take a more useful 

 aspect in connection with book-illustrating than has 

 yet been claimed for it. This is the printing from 

 the relief in ordinary printer's ink, instead of in one 

 special for the purpose. — J. W. W. 



New Photo-engraving Process.— Mr. Duncan 

 Dallas, the patentee of the photo-electric process of 

 engraving of which we some years ago heard much 

 that was promising, but of which we have now long 

 lost sight, is about to introduce a process by which 

 a photographic negative from a drawing made in 

 lines is used to produce blocks for surface-printing. 

 Mr. J. Trail Taylor some time since called our 

 attention to experiments in a similar direction, by 

 which also very successful results have been pro- 

 duced. We hope, therefore, to find several such 

 processes in good working order. — J". W. W. 



Lithographic Process for Tinting Photo- 

 GRAPHS.^Messrs. Southwell Brothers have intro- 

 duced a method of tinting the backgrounds of photo- 

 graphs so as to give the effect of a portrait on a 

 neutral ground with white high lights. The process 

 is thus described in the specification. A good portrait 

 negative has its background carefully blocked out 

 or rendered opaque. In the finished print it is 

 therefore perfectly white, and this is then laid upon 

 a flat board, and covered with a piece of tracing- 

 paper. On this the portrait is carefully outlined 

 with a lead pencil, and the image thus formed is 

 then cut out. Over that portion of the photograph 

 on which the proposed tint is not required, the 

 tracing-paper is fastened with a little gum ; and then 

 the tint is printed over the whole, and the removal 

 of the' tracing-paper with a damp sponge completes 

 the first part of the process so far as regards the 

 background ; if a general tone is required over the 

 whole, a second printing is used. The photograph 

 is next damped between sheets of wet blotting- 

 paper, and a properly-prepared embossing-block is 

 used in a lever or other press, to give a texture to 

 the whole resembling in effect and appearance that 

 of drawing-paper.— /. W. W. 



