﻿Intelligence and Miscellaneous Articles. 245 



not a dolomite. The gold seems to occur chiefly in the calcareous 

 portions of the rock. The Author has also been tempted to suggest 

 a similar origin for the saddle-reefs of the Bendigo gold-field. In 

 all of these cases the train of reasoning is based upon the con- 

 clusions arrived at in his previous paper ' On the Dwindling and 

 Disappearance of Limestones/ He indicates that the stratigraphical 

 relations of the Arkansas novaculites, as described in Mr. Gris wold's 

 Report, are such as to warrant the assumption that limestones once 

 occurred in the position now occupied by beds of novaculite. Many 

 collateral matters are dealt with in the paper which cannot be 

 given in abstract : among them is an attempt to classify quartzites. 



2. ' Note on the Occurrence of Perlitic Cracks in Quartz.' By 

 W. W. Watts, Esq., M.A., E.G.S. 



The Author of this communication described some specimens of 

 the porphyritic pitchstone of Sandy Braes in Antrim, which are 

 deposited in the Museum of Science and Art in Dublin, and in that 

 of Practical Geology in Jermyn Street. They exhibit admirable 

 examples of perlitic structure in the brown glassy matrix and the 

 presence of polygonal, circumferential, and radial cracks is noticed. 

 The porphyritic crystals of quartz are traversed by curved fissures of 

 retreat, not so perfect as those found in the glass, but better than 

 those usually produced by the rapid cooling of Canada balsam. The 

 fissures in the quartz are frequently prolonged into the matrix, 

 undergoing only a very slight and almost imperceptible deviation in 

 direction at the junction. But in addition to this the quartz is 

 often found to act as a centre of strain, the inner cracks of the 

 perlite being wholly in quartz, the next traversing both, and the 

 outer ones in glass only. In other examples the outer cracks of a 

 matrix perlite sometimes enter the quartz, while in others polygonal 

 cracks occur, and join up in, the quartz and give off radial cracks 

 precisely like those of the matrix. These observations lead to the 

 conclusion that the quartz and glass must have contracted at about 

 the same rate, and that the observation of perlitic structure in a 

 rock with trachytic or felsitic matrix by no means proves that the 

 rock is necessarily a devitrified glass. References are given to 

 somewhat similar observations by Eouque and Michel-Levy, and by 

 Iddings. 



XXVII. Intelligence and Miscellaneous Articles. 



ON THE THERMAL BEHAVIOUR OF LIQUIDS. 

 BY PROF. BATTELLI. 



To the Editors of the Philosophical Magazine. 

 Gentlemen, 

 T HAVE been prevented for a considerable time from attending to 

 -*- my usual studies by serious domestic trouble, and thus I was 

 not able at once to read and consider the observations of Professors 



