132 METHOD OF RENDERING GLASS OPAQUE. 



ges attested the fitness of what he would recommend. It was a 

 course of study by which the mind might be formed to reason 

 closely and in a train on the most unquestionable principles : that 

 would habituate the understanding to the contemplation of truth, 

 until it should insensibly contract a deep-rooted veneration for it ; 

 and afford the rational faculties so vigorous an exercise as would 

 qualify the student to transfer his attention to any other department 

 of philosophy, and to range with ease over the most difficult sub- 

 jects of mental research. He should be anticipated in naming the 

 Elements of Mathematics, where in a single proposition there are as 

 many steps of pure reasoning as could be traced throughout a 

 volume of many professed argumentative writers. No one would 

 of course imagine that he contended for the necessity of making all 

 men profound mathematicians, but that they should be early initia- 

 ted into, and completely familiarised with, the method of reasoning 

 pursued in Euclid's demonstrations. 



METHOD OF RENDERING GLASS OPAQUE. 



A correspondent, at page 27, vol. III., of the Museum, enquires 

 the mode of rendering glass opaque. There are several ways of 

 doing this : First, take a piece of flat copper, and a little sand or 

 fine emery made into a very thin paste with water, and with this rub 

 over the glass with a circular motion of the hand ; this will, in a 

 short time, destroy the polish of the surface : instead of copper a 

 piece of Yorkshire frit may be used, but I prefer the former, as it 

 holds the sand better. 



2ndly, In the Artists' Arcanum the following receipt is given : 

 Pulverise a quantity of gum tragacanth, and having previously provi- 

 ded white of eggs well beat and settled as thin as water, mix them 

 together, and let them stand twenty-four hours, or until the gum is 

 dissolved, and lay it on the glass with a soft brush. 



But the best mode is to employ a soft piece of Glaziers' putty, and 

 with this, having first cleaned the glass, dab the surface all over ; 

 allow this to harden twenty-four hours and repeat the process. An 

 ornamental border or other device may then be traced with a sharp 

 pointed piece of deal which will remove the putty and allow the 

 polished surface of the glass to appear. J. N. H. 



Printed and Published by G. Hearder, Buckwell Street, Plymouth. 



