2364. Liquid Spectroscopes

2364.    Liquid Spectroscopes. The use of transparent liquids, such as bisulphide of carbon, for the manufacture of lenses, is making rapid progress on the ground of economy; large pieces of glass, free from flaw and blemish, being difficult to obtain, and expensive. Poggendorffs "Annalen" calls attention to possible disturbances of the accuracy of liquid prisms, the lines in the spectrum varying with the temperature. The divergence, owing to changes of heat and cold, of the lines of solid prisms, is quite insignificant. A glass prism, heated in the sun and then removed to the shade, was observed to possess an increased refractive power as it cooled, while a bisulphide prism exhibited a reversed result. These facts point out the importance of the use of the thermometer in conjunction with the spectroscope, and also show that there is room for great improvement in the manufacture of glass for optical purposes.

2365. Prismatic Diamond Crystals for Windows

2365.     Prismatic Diamond Crystals for Windows. A hot solution of sulphate of magnesia, and a clear solution of gum-arabic, mixed together. Lay it on hot. For a margin or for figures, wipe off the part you wish to remain clear with a wet towel.

2366. To Drill Glass

2366.    To Drill Glass. Wet an ordinary drill with petroleum or benzine; turpentine will answer, but not so well; it will then bore common glass nearly as rapidly as steel. If it is intended to bore through, the glass should be first countersunk on each side with a drill dressed off so as to form a very flat three-sided pyramid. Flint and plate-glass are very difficult to bore. It has been recently ascertained that dilute sulphuric acid is much more effective, "with less wear of the tool, than oil of turpentine. It is stated that at Berlin, glass castings for pump barrels etc., are drilled, planed and bored like iron ones, and in the same lathes and machines, by the aid of sulphuric acid.

2367. To Cut Glass Round or Oval Without a Diamond

2367.    To Cut Glass Round or Oval Without a Diamond. Scratch the glass around the shape you desire with the corner of a file or graver; then, having bent a piece of wire to the same shape, heat it red hot and lay it upon the scratch, sink the glass into cold water just deep enough for the water to come almost on a level with its upper surface.

2368. To Break Glass in any Required Way

2368.  To Break Glass in any Required Way. Dip a piece of worsted thread in spirits of turpentine, wrap it round the glass in the direction required to be broken, and then set fire to the thread, or apply a red hot wire round the glass; if it does not immediately crack, throw cold water on it while the wire remains hot. By this means glass vessels that have been broken may often be fashioned and rendered useful for a variety of purposes.