406 Proceedings of the Royal Irish Academy. 



the side next the rihhon is melted, and that the upper side is not 

 altered, or at least only softened slightly. In some minerals ^vhen the 

 under side is melted the rest of the particle is not supported on it, so 

 that it in its turn comes in contact Tvith the rihhon, and is melted when 

 the rihhon is left at the temperature at which the under part was 

 ohserved to melt, hut in the ease of Olivine and a few other minerals 

 this is not so ; as, when the underside melts, the upper portion is 

 supported on it, and if the temperature is not raised it will stay thus 

 never melting, radiating heat as rapidly as it ahsorbs it. As this 

 temperature is the same as the temperature at which the minutest 

 particles melt, I have put it down as the melting point in the case 

 of Olivine, and several other equally viscous minerals that behave 

 similarly. 



Garnet. — The specimens of Almandine garnet examined were not 

 of any particular interest ; they were slightly viscous, and melted at 

 very much the same temperature. One was found at the junction of 

 the granite and the gneiss near Carrickmines ; it was transparent and 

 dark red. 



Vesuvianite presents no viscosity, and bubbles up at about 1100°. 



Epidoie changes colour as it is heated and bubbles up at about 

 1000°; one specimen of epidote was fibrous, and it melted at a higher 

 temperature than the granular specimen. 



In Meonite, Nepheline, Sodcdite, and Leucite nothing remarkable 

 was observed ; they were all observed to bubble slightly, except 

 Nepheline, when fused. 



The Felspars. — Two specimens of Adulaiia were examined, both 

 transparent, and melting practically at the same temperature. Adularia 

 bubbles up at about 1230°, which the other felspars have not been 

 observed to do ; it can thus easily be recognised. All the felspars are 

 viscous to a large degree ; a margin of 15° is allowed from the time 

 the substance is first observed to soften till it melts. The figures 

 given are those at which the smallest particles of the dust were 

 observed to be melted on the ribbon. When melted they look more 

 transparent. This is a very good means of observing when the 

 substance is melted, for then the ribbon looks like a strip of paper 

 with a number of pinholes in it held up to the light, and after a few 

 trials it is possible to catch the temperature at which the pinhole 

 appearance first occurs. Before this temperature is reached, however, 

 the little particles are observed to tumble about the ribbon showing that 

 they are going through a period of viscosity before the melting point 

 is reached. The felspars are not distinguishable from one another by 



