74 PHILOSOPHICAL TRANSACTIONS. [aNNOIJSS. 



model of the Newtonian telescope, in which he has been greatly assisted by 

 that excellent workman, Mr. Scarlet, jun. As to the effects of this instru- 

 ment, it magnifies from the distance of Q to 24 inches. 



Fig. 1, pi. 4, represents the entire microscope, mounted on its pedestal, on 

 a proper joint, contrived so as to direct the instrument towards any object. 



Fig. 2, the section of the instrument ; in which ab is the larger concave 

 metalline speculum ; CD the lesser concave metalline speculum ; ef a hollow 

 brass screw, to fasten in the 1st dioptrical glass, or plano-convex lens; gh an- 

 other screw fastening on the hollow cylinder efik (in which the dioptric glasses 

 are contained) to the body of the microscope ; ik a cap with a small perfora- 

 tion, serving as an aperture to the eye-glass, or 2d lens, convex on both sides; 

 ML is a long screw passing through the nuts p and v, serving to bring the small 

 speculum to a proper distance from the larger; Na a sliding piece moved by the 

 screw, carrying the stem an, and the little speculum cd ; yx a screw for the 

 cap at fig. 3 ; that at fig. 4, is to be screwed on the aperture jk. 



Fig. 5, shows the construction of the microscope ; in which i is an object 

 supposed erect ; from which rays falling on the speculum ab, will be reflected 

 to the focus k, where they will form an inverted image ; and being reflected by 

 the small speculum cd, they will pass through the perforation of the great 

 speculum, and falling on the plano-convex glass ef, converge again, and form 

 an erect image at I ; which being brought very near to the eye, and so con- 

 siderably magnified, will be distinctly seen through the eye-glass gh. 



yin Account of the Standard Measures preserved in the Capitol at Rome. By 

 Martin Folhes, Esq. V. P. R. S. N° 442, p. 262. 



In the wall of the capitol is a fair stone of white marble, of the length of 8 

 feet 5 inches English, and of the breadth of 1 foot 9-f inches ; on which are 

 inscribed the standards of several measures with these respective inscriptions : 

 Piede Ro : Pal. iiii. One. xii. Deti xvi. 



Piede Greco. 

 Canna di Architet. Palmi x. 

 Staiolo Pal. v. Quar. iii. 

 Canna di Merca. Palmi otto d'altra misura. 

 Braccio di Merc. Pal. iii. d'altra misura 



Braccio di Tessito di Tela. 

 Curante Lu. Poeto. 

 The lines, that represent these measures, are cut in the marble, pretty deep; 

 but as they have, consequently, a considerable thickness, it is somewhat difii- 



