'248 VHILOSOPHICAL TRANSACTIONS. [aNNO 1738. 



If the blow be given against the ceiling, or any horizontal body, with the 

 upper end of the bar, the same virtue will be communicated as before. 



This will likewise happen, if the upper or lower end of the bar be struck 

 with a hammer or mallet; whether the blow be given end-wise or at right angles 

 to the bar : nay, though it should be given in the middle of the bar ; the 

 position of the bar at receiving the blow being all that is requisite; for if you 

 give the bar only a jerk, or shake in that vertical position, it will receive the 

 virtue, as if there were in the iron several threads or beards fixed at one end, 

 as M. Du Fay supposes, which the blow or shake laid all one way, and which 

 were placed the other way by inverting the bar, and then giving it a shake 

 or blow. 



When the bar is placed horizontally, a blow in the middle destroys its 

 virtue. 



Of an Antique Metal Stamp, in the Collection of his Grace Charles Duke of 

 Richmond, Lenox and Aubigny, F. R. S. &c. being one of the Instances, 

 how near the Romans had arrived to the Art of Printing ; with some Re- 

 marks by C. Mortimer, M. D. Sec. R. S. Land. N" 450, p. 388. 



Since arts and sciences, especially statuary and sculpture, were arrived at so 

 great perfection, when the Roman empire was in its glory, as the many beau- 

 tiful statues, the exquisite intaglias, and the fine medals, which time has de- 

 livered down to us, sufficiently evince ; it is much to be wondered at, that 

 they never hit upon the method of printing books. 



The dies they made for their coins, and their stamping them on the metal, 

 was in reality printing on metal ; their seals cut in cornelians and agates, and 

 their pressing them on dough and soft wax, was another sort of printing; and 

 a third sort was the marking their earthen vessels, while the clay was soft, with 

 the name of the potter, or the owner the vessel was made for. These being 

 of a larger size, were properly called signa; the seals cut in stone were called 

 sigilla; sigillum being a diminutive of signum, as tigillum is of lignum: but 

 the later and more barbarous Latinists have formed the diminutive of signum 

 into signetum; and if a very small pocket-seal, they have called it signaculum. 

 See Joh. Mich. Heinecius de Sigillis. Francof. 1709, fol. p. 16, et seq. 



The learned Montfaucon, among his immense treasures of antiquities, in 

 his Antiquite expliquee, Tom. 3, Part. id. Chap. 12, gives the figures and 

 descriptions of several of these larger sigilla or signa, on which he says, the 

 names were all cut in hollow in capital letters; and he imagines their use to 



