Page:The wonders of optics (1869).djvu/101

 will be coloured with these figures in the tint of the wall or fabric upon which they fall, yellowish colours of course escaping the transformation. If nitrate of strontia be substituted for the salt, a crimson tint will be spread over everything. In fact, a lamp prepared in this way will form a source of endless amusement. It is not necessary to use alcohol for the purpose; wood-spirit or methylated alcohol will serve the purpose equally well. If a lamp is not to be had, a few pieces of cotton-wool, tied on wires and dipped in the salted spirit, will do almost as well.