263 Intelligence and Miscellaneous Articles. 



I. II. 



Gold 87-78 87-77 



Silver 6-07 6-54 



Peroxide of iron by loss 6-15 5-69 



100-00 100-00 



"The alloy obtained was of specific gravity 18-83, and gave by 



analysis — 



I. II* 



Gold 93-53 93-06 



Silver 6-47 694 



100-00 10000 



" Another sample of the alloy submitted to analysis, gave — 



Gold 96-42 



Silver 3-58 



«Ti ^ i o 117 1 T> 13 " Andrew D. Thomas." 



" Patent Copper Works, Burra Burra, 



June 1850." 



POLARIZATION BY CAOUTCHOUC AND GUTTA PERCHA. 

 BY PROF. CHAS. G. PAGE, M.D. 

 Gutta percha, when rolled into thin sheets or drawn into ropes, 

 comports itself like a fibrous substance, which is not the case with 

 caoutchouc. A strip cut from a thin sheet of gutta percha may be 

 stretched considerably in one direction, that is, in a line with the 

 fibre, but any attempt to stretch it across this line is followed at 

 once by a rupture. It is not so with a sheet of caoutchouc, which 

 will stretch equally well in all directions. On examination of thin 

 sheets of these two substances — so far believed to be isomerical — a 

 marked difference of texture is at once perceived. The caoutchouc 

 gives little or no change of colour, while the gutta percha exhibits 

 a beautiful spectacle. It appears to be built up of prisms of every 

 variety of hue, and, as it were, fused into each other. It resembles 

 more nearly some specimens of ice which I have examined than 

 anything else. The caoutchouc and gutta percha must be kept under 

 considerable tension during the examination. 



There is one mode, however, in which I have produced some fine 

 figures by means of caoutchouc. The caoutchouc is made into little 

 balloons in the following manner:— A very thin sheet is tied over 

 the end of a tube of one-half inch bore, and the caoutchouc blown 

 out into a ball and firmly tied just beyond the end of the tube with 

 a piece of silk. They can with a little practice be very conveniently 

 made by the mouth. The caoutchouc is drawn over the open mouth, 

 and by strong suction it is forced in, filling the mouth, when the 

 lips and teeth are compressed over the outer portions so as to form a 

 neck, -which is at once twisted up by the fingers and secured with a 



• Second analysis done by Mr. Frederick Walters. 



1 



