430 Mr. W. Ferguson on the occurrence of Chalk Flints 



Derby (where the apparatus above described was made), has 

 constructed a gutta percha electrical machine, similar in prin- 

 ciple, but with several improvements. 



In this machine a thicker description of gutta percha band 

 is employed. The upper and lower rollers are of equal dia- 

 meter; and the rubbers, which are brushes of bristles, four in 

 number, are placed outside the band and opposite to the axis 

 of each roller. 



A double conductor connected by a curved brass rod pass- 

 ing over the top of the machine is applied, similar in form to 

 the conductor of the plate-glass machines ; and there is an 

 ingenious tightening apparatus, to correct the expansion and 

 contraction of the gutta percha band. 



The machine is exceedingly handsome in appearance ; and 

 the employment of the thicker gutta percha removes the diffi- 

 culty experienced in the former apparatus from the band be- 

 coming folded. 



The band is about four inches wide ; and the electricity 

 given off appears to be of higher intensity, and, under favour- 

 able states of the weather, nearly as much in quantity as that 

 of an ordinary plate-glass machine. 



The improvements above described are all due to John 

 Westmoreland; and this machine (which is beautifully finished, 

 and is, I believe, intended for the Exhibition of 1851) is the 

 result of his labours after the usual hours of work in Mr. 

 Davis's establishment. 



W. H. B. 



Derby, Nov. 14, 1850. 



LVI. Notice of the occurrence of Chalk Flints and Greensand 

 Fossils in Aberdeenshire, By William Ferguson, Esq*. 



ANY years have elapsed since it was first noticed that 

 quantities of flints containing organic remains charac- 

 teristic of the chalk, as well as certain organic remains be- 

 longing to the greensand formation, existed in Aberdeenshire. 

 Dr. Knight, of Mareschal College, Aberdeen, was aware of 

 the fact, and through him it was communicated to Dr. Thomas 

 Thomson of Glasgow College nearly twenty years ago. Mr. 

 Christie of Banff published a notice upon the occurrence of 

 flints at Boyndie Bay, Banffshire, in the Edinburgh Philoso- 

 phical Magazine for 1841 ; and a paper on the same subject, 

 of which the present is a condensed view, was read before the 

 Philosophical Society of Glasgow, Session 1848-1849. Since 



* Communicated by the Author. 



