440 PHILOSOPHICAL TRANSACTIONS. [aNNO 1747-8. 



several petrified fossil shells ; which clearly show that its formation was of a more 

 ancient date than the age of these muscles can admit of. Secondly, that the 

 holes on the surface are narrower, in general, than the cavity in which the fish 

 lies ; and which demonstrates that they enter young, and are capable of increas- 

 ing their room as they grow larger, by abrading the sides of their cells : and this 

 is fiirther apparent by the sandy matter found in the bottoms of those cells, which 

 the fish cannot well get rid of, when it happens that the orifice is higher than 

 the bottom ; abundance of which was observed in some of the holes ; and which 

 is easily thrown quite out, when the orifice is depending ; for in these they ob- 

 served none : and this is further confirmed by what Dr. Woodward relates in 

 the first vol. of his Catalogue, p. 25, that certain pillars of white Carrara marble 

 taken out of the sea, on the coast of Leghorn, after lying there a number of 

 years, were destroyed by the boring of these pholades. 



As to the manner of their penetrating the stones, he cannot give the least ac- 

 count of it. 



An Account of the Experiments made to discover whether the Electrical Power, 

 when the Conductors of it were not supported by Electrics per se, would be 

 Sensible at Great Distances : with an Inquiry concerning the respective F^elo- 

 cities of Electricity and Sound : to which is added an Appendix, containing 

 some further Inquiries into the Nature and Properties of Electricity. By Mr, 

 fVm. Watson, F.R.S. N° 485, p. 49. 



In a former paper Mr. W. took notice, that among the many surprising pro- 

 perties of electricity, none was more remarkable, than that the electrical power, 

 accumulated in any non-electric matter contained in a glass phial, described on 

 its explosion a circuit through any line of substances non-electrical in a consider- 

 able degree ; if one end of it was in contact with the external surface of this 

 phial, and the other end on the explosion touched either the electrified gun- 

 barrel, to which the phial in charging was usually connected, or the iron hook 

 always fitted in it. This circuit, where the non-electric substances, which hap- 

 pen to be between the outside of the phial and its hook, conduct electricity 

 equally well, is always described in the shortest route possible; but if they con- 

 duct differently, this circuit is always formed through the best conductor, how 

 great soever its length is, rather than through one which conducts not so well, 

 though of much less extent. 



It has been found, that in proportion as bodies are susceptible of having elec- 

 tricity excited in them by friction, in that proportion they are less fit to conduct 

 it to other bodies ; in consequence, of all the substances we are acquainted with, 

 metals, conduct best the electrical powers ; for which reason the circuit before 



