•346 Bones of Mammalia in the Crag. 



or socket, with a flat circular head to it, nearly equal in thick- 

 ness to the stage ; and of cementing to it with shell lac, a plate 

 of glass, which lies upon the stage, and swings or turns upon 

 that as a centre, and thus affords the opposite crossing move- 

 ment required, in a most complete and effectual manner. 1 

 believe that such valuable results were never before attained 

 in so facile a way. And indeed it would seem as if every- 

 thing had been expressly provided for the occasion, and only 

 needed my wish to be possessed of this truly desirable pro- 

 perty of moving an object, even of considerable size, in every 

 direction, with the utmost freedom. I have cemented a small 

 flat ivory button upon the right hand corner of the glass plate, 

 by way of handle to move it by. 



I have likewise effected the important object of graduating 

 the light from the plane or concave specula which slide upon 

 the stem, in a most simple and efficient manner. This I have 

 lately accomplished as follows ; a double convex lens, mount- 

 ed in a screwed cell, was formerly slidden upon the stem up- 

 wards and downwards, to concentrate or diffuse the light from 

 the specula. I however had laid this aside as useless. I now 

 have fitted a short tube, with a diaphragm, or circular hole, at 

 its upper end, a quarter of an inch in diameter, into a metal 

 cone which used to be fixed upon the cell, under the stage, to 

 lessen the light occasionally ; and this cone, so altered, is now 

 fixed to the screwed ring of the condensing lens, (but which 

 lens, as before mentioned, I had laid aside), and can be slid- 

 den up and down on the stem, nearer to or farther from, the 

 plane or concave speculum and the stage, at pleasure ; and 

 thus graduate the light cast by them upon the objects, in a 

 most complete manner. The length of the tube fixed within 

 the cone is three quarters of an inch ; and the aperture in the 

 cone below it, is three eighths of an inch: the diameter of the 

 cone itself being an inch and a half; and the whole is well 

 blackened with a dull coat of varnish. And thus the passage 

 of the light from the specula below to the stage, is effected 

 only through the short tube, and its upper and lower aper- 

 tures, the central rays only being suffered to pass ; an advan- 

 tage I need not dwell upon. — Thomas Gill. — 125, Central 

 Strand, London ; March 23rd, 1838. 



Bones of Mammalia in the Crag. — Your worthy correspon- 

 dent, the Rev. W. B. Clarke, has, by his communication at 

 p. 162 of the number for March, reminded me of some bones 

 which I obtained from a person who told me he took them out 

 of the crag cliff at Felixstow, on the Suffolk coast. 



This was in November last. I have since visited that lo- 

 cality, and the spot was pointed out to me ; in making further 



