Progress of Invention. 67 



count of its clearness, the latter on account of its injurious effect 

 on the workpeople ; and yet no substitute for them was discovered. 

 M. Gaultier de Claubry has found out a very simple mode of ren- 

 dering these dyes soluble in water. It may be remarked that their 

 solution is attended with peculiar difficulties, on account of their 

 being, in many instances, composed of constituents of very dif- 

 ferent solubility. Thus the aniline violet contains red elements 

 which are soluble in various fluids, and blue, which are with diffi- 

 culty soluble at all. During his researches, M. Claubry ascertained 

 that there are many substances which impart to water the power 

 of dissolving them. Thus gums, mucilages, soaps, glucose, dextrine, 

 the jellies of different feculse, lichens, and fuci. When, for example, 

 Egyptian soap-wort is used, and it answers extremely well, it may 

 be triturated with the colouring matter. Boiling water is then to 

 be added in successive doses — each being removed before the next 

 is added — as long as anything remains undissolved ; the action of 

 the different portions of fluid being aided by shaking, and the clear 

 solutions obtained being removed by decantation. All the solutions 

 must, in the end, be mixed together, as the earlier ones will take 

 up chiefly the more soluble constituents : and thus a perfectly pure 

 tint, quite unchanged by the process, will be obtained. The mode 

 of proceeding may be modified in various ways. Thus, if it is 

 considered desirable to use some alcohol, the soap-worfc may be 

 employed first, and the alcohol towards the end of the solution, or 

 vice versa. 



Portable Submarine Light. — The electric light has very often 

 been used for producing illumination under water ; the charcoal 

 points being inclosed in a water-tight receiver, and the battery 

 being placed in a boat, etc. But this arrangement is objectionable ; 

 it is very costly, the apparatus is extremely liable to disarrangement, 

 and is difficult to be manipulated; moreover, the light, for many 

 purposes is far too intense. M. Paul Gervais has devised a method 

 of applying an apparatus, very similar to that proposed for use in 

 mines,* to submarine illumination. It consists of a Geisler tube, 

 of an appropriate form, filled with carbonic acid, and inclosed in a 

 stout water-tight glass cylinder, and capable of being put in con- 

 nection, at pleasure, with a battery and coil, which are within a 

 water-tight case that is easily portable. In constructing this 

 apparatus, M. Gervais obtained the assistance of Ruhmkorff, who 

 is also at present carrying out some improvements, that are 

 expected to render it still more practically useful. The light 

 emitted by it is said A r ery closely to resemble that of phosphorescent 

 animals, except that it is more intense ; even when several yards 

 under water it can be perceived at a considerable distance. The 

 instrument used has been kept nine hours at a time under water, 

 and six of these in action ; indeed, there does not seem any limit to 

 the time during which it may be in operation. 



* Intellectual Observed., Mo. xxxviii. p. 146. 



