V 



260 Intelligence and Miscellaneous Articles. 



Other species, such as Orthis Mickelwi* formerly supposed to be 

 peculiar to the ' Upper Grey Limestone/ have been found at the 

 base of the ' Middle White Limestone,' at the Flagstaff Quarry on 

 the Marine Drive, near the Happy Valley. 



The dolomitization of the Carboniferous Limestone is remarkable, 

 and almost peculiar to that around Llandudno, though it also occurs 

 at Penmon in Anglesey. The ' Lower Brown Limestone ' has been 

 almost entirely converted into dolomite, and portions of the over- 

 lying subdivisions. The filling' of the faults has often been changed 

 into dolomite, and the alteration of the Limestone has generally been 

 very capricious: the author's opinion being that the change took 

 place after the dislocation of the strata in post-Triassic times, 



2. ' The Graptolite-Fauna of the Skiddaw Slates.' Bv Miss G. 

 L. Elles. 



XXV. Intelligence and Miscellaneous Articles. 



To the Editors of the Philosophical Magazine. 

 Gentlemen, 



f\& page 183 of the February 1898 number of your Magazine 

 " appears an article by Frederick Jervis-Smith, M.A., F.R.S., 

 Millard and University Lecturer on Mechanics, Oxford, entitled 

 "A New Method of Measuring the Torsional Angle of a Eotating 

 Shaft or Spiral Spring." 



The method which Mr. Smith descrihes is precisely the same as 

 was employed for this purpose in my laboratory in 1885-86. 



An account was presented to the American Society of Mechanical 

 Engineers in November 1886, and this account was published in 

 volume viii. of the Transactions, pages 130-139. 



In this article on the " Strength of Shafting subjected to both 

 twisting and bending " the description of the apparatus for meas- 

 uring the angle of twist is given on pages 138 and 139 ; and a cut 

 of the entire apparatus is on page 134. 



Moreover, in London Engineering of January 14th, 1887, page 

 26, a portion of my communication to the American Society of 

 Mechanical Engineers is published, including a copy of the cut of 

 the entire apparatus, though the written description of the portion 

 used for measuring the angle of twist is omitted. 



Evidently if Mr. Smith had been aware of these published 

 articles, he would not have called the method he describes new. 



I will add that this portion of the apparatus was mainly devised 

 by Mr. Theodore E. Foster, who was at that time a student in the 

 department. 



I am, Gentlemen, 

 Yours truly, 



Gaetako Lasza. 



Prof, of Applied Mechanics, 

 in charge of Dept. of Mechanical Engineering, 

 Massachusetts Institute of Technology. 



