142 Intelligence and Miscellaneous Articles. 



questions are raised concerning the latter : — (1) Can a succession be 

 traced below the Purple Slates drailar to that which the author has 

 described as occurring in Caernarvonshire ? and (2) Whero is the 

 most natural break in the series, aud docs it show an unconformity? 



With reference to the first question, the author gives his reasons 

 for concluding that, as far as the succession is seen in the Harlech 

 area, it is similar to that of Caernarvonshire. A group of Purple 

 Slates is described which so closely resembles the Llanbcris and 

 Penrhyn Slates that he considered himself justified in definitely 

 correlating them with those slates. lielow these are slaty grey- 

 wackes, which, if not identical with those of Caernarvonshire, bear 

 a greater resemblance to them than any other part of the series 

 does. No older beds are seen. Above the Purple Slates are the 

 Harlech Grits proper. 



In discussing the second question, the author describes con- 

 glomeratic beds occurring some distance above the base of these 

 Harlech Grits ; but at Pont Llyn-y-Crom the junction between them 

 and the underlying Purple Slates shows features recalling what is 

 seen at Bronllwyd. He discusses the possible existence of an 

 unconformity at the base of these grits, and concludes that on the 

 whole the phenomena point, though not very strongly, to au 

 unconformity of no great importance. 



The concluding part of the paper is occupied with a consideration 

 of the question of classification of the Cambiian strata and those in 

 juxtaposition with them. 



XIII. Intelligence and Miscellaneous Articles. 



ON THE VELOCITY OF SOUND IN GASES. 



To the Editors of the Philosophical Magazine. 



Gentlemen, 



T READ in No. 232, September 1894, of the Philosophical 

 -*- Magazine a paper by Mr. Webster Low, " On the Velocity 

 of Sound in Air, Gases, and Vapours for Pure Notes of different 

 Pitch." I deem it important to acquaint the Editors of the Philo- 

 sophical Magazine that as long ago as 1881 1 used a method nearly 

 identical with Mr. Low's in order to determine the velocity of 

 sound in some gases (air, C0 2 , N 2 0), and particularly in chlorine, 

 its value for this gas being till that time quite unknown. My 

 results were published in the Acts of the Venetian Institute*, 

 and in abstract in other periodicals t. As to chlorine, which was 



* Atti del JR. Istituto Veneto di Scienze, Letter e edArti, seiie 5, vol. viii. 

 p. 494, and serie 7, vol. iv. p. 1113. 



t Journal de Phynque tkeorique et appliquee, vol. x. p. 410 (1S81) ; 

 Beibldtter zu den Annalcn der Physih unci Chemie, vol. v. p. 564 (1881). 



