24 



EECEEATIVE SCIEI^CE. 



them further in. Gmelin and the authors al- 

 ready named. 



And now, in conclusion, to consider some 

 of the applications of silica in the form of 

 Trater-glass to the arts. First, as most inte- 

 resting to us, it is proposed to make careful 

 photographic experiments with varieties of 

 water-glass, adding more or less sUica, as may 

 be deemed fit. Water-glass has heen also 

 proposed (and is undergoing fair trial), in 

 order to protect building stones from decay. 

 The expectation is that water-glass, applied as 

 a wash, will hare its silica deposited by atmo- 

 spheric carbonic acid, in minute adherent par- 

 ticles, upon the surface of the stone, which 

 will thus be shielded by a flinty substance 

 from the acids which smoky rain brings down 

 in large towns ; and where carbonate of lime 

 exists in the building stone, a further action 

 is expected from the formation of an insoluble 

 silicate of lime, another protective agent. 

 The decaying surfaces in the cathedral of 

 Notre Dame, in Paris, the new Houses of Par- 

 liament, at Westminster, and many other simi- 

 lar buildings have been thus treated. Then it 

 has been proposed to mix soluble glass with 

 mortars, to enable them to set under water, 

 by virtue of the insoluble silicates, which 

 would form under circumstances of contact 

 between water-glass and the materials used. 

 Another and very important (for the fine arts) 

 application is in the stereochrome system of 

 painting, invented by Puchs, and worked out 

 successfully by Kaulbach in Germany, and 

 Kuhlmann at LUle. The principle is to pre- 

 pare a surface of cement or stone or slate in 

 a manner proper to receive dry colours, and 

 then to fix these colours on the wall or surface 

 by means of a varnish of the soluble glass, 

 which is syringed on, and left to dry. In a 

 short time the carbonic acid of the air and the 

 earths in the surface throw down the silica, or 

 flint, the alkali partly combining ; or it efflo- 

 resces out, and is easily washed ofi", the picture 

 remaining adherent, and only removeable by 

 mechanical disintegration. Experiments made 



in exposed places, as to weather, have proved 

 to be perfectly successful. A crucial experi- 

 ment was made at Berlin by suspending a ste- 

 reochrome painting for twelve months in the 

 open air, under the principal chimney of the 

 New Museum at Berlin. During that time it 

 was exposed to sunshine, mist, snow, and rain, 

 and nevertheless retained its full brilliancy 

 of colour. 



To allude again to photography, it may be 

 observed that from the description given of 

 the behaviour of water-glass in a concentrated 

 form applied to paper — its acting as a cement, 

 or glue — it will be advisable to try its powers 

 in the preparation of paper previous to the for- 

 mation of the photographic image. Its action 

 when mixed with gelatine and tanning mate- 

 rials also seems worthy of study by the pho- 

 tographer. It should be applied in a dilute 

 form to the finished photograph, as a concen- 

 trated solution is reported to dry pulverulent. 

 Bodies that do not cement well together with 

 Avater-glass alone, can be made to cement by 

 the addition of other substances. The various 

 affinities of water-glass are very curious and 

 interesting, and deserve minute study. Wa- 

 ter-glass has been used successfully in paint- 

 ing upon glass, and it is in this direction 

 that we also hope for valuable results to 

 the photographer. The true way is to let 

 each one in his own department endeavour to 

 apply water-glass and its sUicious correlatives 

 in the best way his ingenuity can devise. It 

 is confessedly a new and unworked subject, 

 on which nothing very definite ought at pre- 

 sent to be pronounced ; but surely enough is 

 here ofiered to stimulate to further trials. 

 Wood and textile fabrics are rendered less 

 combustible by the application of water- 

 glass, and we have been informed by Dr. 

 Miiller that a glass-maker in Germany var- 

 nished the wooden roof blocks of an entire 

 village with water-glass, now thirty years 

 ago, to render them less liable to accidental 

 combustion. Theatrical dresses and proper- 

 ties have also been alleged to be suitable for 



