At one time articles of this kind were frequently seen as curiosities, such as tumblers that could be dropped on the floor without breaking, etc., but these articles generally ended by receiving a slight scratch or chip and promptly falling into fragments. As a matter of fact, however, some tempered glass is actually manufactured by the firm of Siemens at the present time for special purposes. De la Bastie’s process was tried in England, and some success was claimed for it; but it is not in commercial operation at the present time, and never appears to have attained any great importance. _Massive Glass._--Enthusiasts for the extension of the use of glass have endeavoured to apply it to a great variety of purposes, including the construction of buildings and the paving of streets. In the former case, which was exemplified at the Paris Exhibition of 1900, advantage was taken of the light-transmitting power of the material, but although the buildings erected with large blocks of cast glass were not displeasing in effect, this use has not found any considerable extension. For paving purposes, the hardness and durability of glass are the only useful qualities, and here also--although several trials have been made in France--no signs of any considerable application of the new products are as yet visible. What has been said above with reference to the injurious character of glass dust applies, further, to glass pavements, since their natural wear would result in the formation of considerable quantities of this dust. The advocates of glass paving, however, suggest that the hardness of glass would greatly reduce the actual amount of wear, and that consequently the dust would be reduced considerably. This is a matter which prolonged experience alone can decide, but it does not seem obvious that glass blocks should wear more slowly than stone setts made of good granite, for example. On the other hand, the glass blocks could probably be produced more cheaply, since the labour of cutting to size would be obviated by casting the blocks to the desired dimensions. Water-glass, or silicate of soda or potash is perhaps scarcely to be classed under the heading of “Glass Manufacture” at all, but it bears a certain relationship to glass in several ways. Thus one of the modes of manufacturing water-glass is by the fusion of sand and alkali in tank furnaces somewhat resembling those used for glass production; the fused silicate, moreover, solidifies as a vitreous mass, in which respect it also resembles such substances as borax, etc. The uses of silicate of soda and potash are, however, so far removed from the field of glass-manufacture that we cannot enter into them here.