D}\ C. Davison — The Pendleton Earth- sJiahe. 171 



observations incidental to other work, and I only wish I knew 

 where the special subject has been studied and described. The 

 hydro thermal phenomena of the Devonian diabases, of the 

 Devonshire quartz- and mica-schists, and of the green rocks, and 

 of the so-called pegmatite felspathic veins connected with the green 

 rocks — these present to my mind the most interesting problems in 

 the debatable Devonshire area, and, compared with them, the 

 question as to whether the schists are Archaean or Devonian, or, 

 as has recently been suggested, any possible age between those 

 geological horizons, does not matter the toss up of a bad half- 

 penny. Certainly, if neither Archeean nor Devonian I do not care 

 what they are. 



I may perhaps explain that I have never possessed a first-rate 

 petrological microscope, and that for the work above referred to the 

 small students' microscopes are about as useful as a pocket lens, 

 as a mechanical stage and a somewhat elaborate achromatic 

 condenser are as essential as are high-powered objectives. But the 

 old microscopes with these fittings are lacking in other advantages. 

 This fact, in addition to my not being well grounded in the 

 identification of minerals, makes it impossible for me to attempt 

 any difficult work myself, and that is really the reason why I have 

 so often pressed these questions upon others, when every motive of 

 self-interest would have bade me avoid unpopular doctrines and 

 keep to the beaten track. 



The motion of bubbles is the easiest proof of the presence of fluid.. 

 The following device, to induce a bubble to move, may not be known 

 to all microscopists. If the substage condenser is furnished with 

 a rotating diaphragm, to allow of oblique light from any point, such 

 a diaphragm, if rotated under strong lamp light, will often make 

 a bubble move owing to the heat thrown laterally upon the fluid 

 inclusion. 



Considering the attention paid to the subject of superheated water 

 by Dr. Sorby and my eminent namesake, the late Dr. Sterry Hunt, 

 more than a quarter of a centui'y ago, it is most remarkable that the 

 investigation has not been followed up with more vigour and 

 determination by their successors. It is well worth conquering. 



V. — The Pendleton Earth-shake of November 2oTn, 1905. 

 By Charles Davison, Sc.D., F.G.S. 



PENDLETON lies on the north-west side of Manchester and 

 within the borough of Salford, and is traversed by the well- 

 known Pendleton or Irvvell Valley fault, a fault which has been traced 

 for more than twenty miles from the neighbourhood of Bolton to 

 that of Poynton in Cheshire. The fault is still slowly growing, for, 

 on February 10th, 1889, a slip near Bolton gave rise to an earth- 

 quake of intensity 6, felt over an area of about 2,500 square miles.' 

 Small superficial movements may also be taking place close to 



1 Geol. Mag., Dec. Ill, Vol. YIII (1S91), pp. 306-316. 



