224 



HARDWICKE'S SCIENCE-GOSSIP. 



[Oct. 1, 186S. 



intermediate between the two ? Or must we admit 

 that probably the creature had lost its two longer 

 arms in the combat which we suppose it to have 

 sustained previous to the attack made on it by the 

 crew of the Alecto? This last is the view taken by 

 those eminent malacologists MM. Crosse and 

 Eischer, who have in consequence consigned it to 

 the genus Loligo, under the name of 'Loligo 

 Bouyeri. ' " 



Such is the account given of this wondrous 

 specimen of a cephalopod by M. Eredol. As 

 regards the gigantic mandible said by him to be 

 preserved in the College of Surgeons' Museum, the 

 assertion might be easily verified or refuted by some 

 reader of Science Gossip familiar with that insti- 

 tution. 



Clifton. W. W. Spicek. 



TO COLOUR PHOTOGRAPHS OE 

 NATURAL OBJECTS. 



MANY of the readers of Science-Gossip have 

 doubtless observed the numerous coloured 

 photographs sold at a cheap rate in London, par- 

 ticularly of flowers, birds, and insects, which are 

 mostly done in Erance or Germany. The effect of 

 some of these is good. 



Having a number of photographs I wanted co- 

 loured, I induced a friend to try ordinary trans- 

 parent water-colours on them. "With a lightly- 

 printed photograph good effects were obtained, but 

 not without much labour, — in fact, an amount that 

 would render the process inapplicable for illustrated 

 books, on the ground of expense. I at last got a set 

 of the American liquid colours, — namely, yellow of 

 a chryso-beryl hue, mauve, scarlet, rose, brown, 

 greeD, and blue. These are clear solutions, having 

 more analogy with stains or dyes than with water- 

 colours. I had coloured several large plates of 

 precious stones, photographed from nature, and 

 printed on albumenized paper : more transparency 

 and depth of colour is, I think, attainable by this 

 plan than by any other. We fancy we can almost 

 lift the stones off the paper ; they are clearly a step 

 in advance of the finest steel mezzotint engrav- 

 ings coloured by hand. The use of these colours 

 requires little knowledge of painting ; some people 

 say the less the better, for the qualities of the 

 colours arc so different. They arc, however, easy 

 to use when their properties become known. The 

 following precious stones I had coloured with them 

 with great success : — chryso-beryl, emerald, ruby, 

 chrysolite, carbuncle, amethyst, topaz, jacinth, and 

 sapphire. There is no deep yellow sold with these 

 colours. I make a splendid stain with saffron, — in 

 fact, a tincture of it, in spirit of wine. This, ac- 

 cording to its intensity, will give us a colour from 

 transparent light topaz-yellow to chrome-orange. 



I wish some of your chemical readers would suggest 

 other colours, — among them a transparent black. 

 Asphaltum dissolved in benzine is the best I know ; 

 but this is too opaque. 



These liquid colours will hardly ever bear dilution 

 with water. Spirit of wine will answer with some. 

 They can rarely be mixed, and cannot be washed 

 off. They will not flow over the albumenized paper, 

 unless it is sized with such as Newman's prepara- 

 tion for sizing photographs, which I suspect to be 

 only thin parchment size, with a trace of ox-gall. 

 Negretti would keep it. The best way of using the 

 colours would be, not from a palette or dish, but 

 from small bottles, pouring a few drops into one as 

 required for immediate use. Ox-gall should be at 

 hand: of this the limpid, colourless extract is the 

 best. Its use is to remove greasiness from the 

 paper, and give concentration and intensity to 

 colours. With plenty of ox-gall, I believe you 

 could paint with these colours on collodion film. 

 I tried the German plan of touching negatives with 

 a blacklead-pencil or cobalt : this is much done in 

 England ; but it failed with me, my marks printing 

 through. When desiring to give the effect of a 

 compound colour, I put on first a wash of one 

 solution and then of another, letting each dry first. 

 I should consider it necessary to rebottle the solu- 

 tions in stoppered bottles if travelling is contem- 

 plated, especially in warm weather. The corks are 

 soon decomposed. Put melted caoutchouc round 

 and over the stoppers, and tie them over, and you 

 will be secure from leakage or adhesion. 



The strongest possible tincture of saffron, made 

 cold with spirit of wine, squeezed and saturated 

 with fresh saffron three or four times, is the mag- 

 nificent deep yellow I use. Several of Judson's 

 simple dyes, in sixpenny bottles, will likewise 

 answer. The maize and orange are particularly 

 good. 



The best green I found was made by mixing a 

 solution of Prussian blue (not an acid solution) 

 with the tincture of saffron : it is difficult to use, as 

 the Prussian blue precipitates, and requires frequent 

 shaking. I should like to find out a clear emerald- 

 green neutral solution, and one also of the budding 

 twig colour and the green apple. 



I have mentioned these little details, thinking 

 they might be useful to some of the many who want 

 to preserve colour in" photographic representations. 



C. 0. G. Napier. 



Smooth Einger-grass. — I enclose a few speci- 

 mens of that rare British plant, the Smooth Finger- 

 grass {Digitaria humifusa). I found it growing near 

 to a plant of the Sweet Basel, in the kitchen garden ; 

 consequently, I consider it to have been introduced 

 with continental seeds, not having observed it iu 

 this neighbourhood before. — C. Wood, Duhclch. 



