(8jS) 
fee what is almoft incredible, Befides which there are delirer'd 
in it the Practical Rules for working Spe&acles for all forts of 
fights, and efpecially T elefcspical GlafTes for obferving the Pla- 
nets and Fixed Stars by Sea aad Land 3 and others, to magnifie 
thefmalleft of near Obje&s thoufands of times. 
There being, among the reft, defcribed by the Author a par- 
ticular way, call'd by him New and Univerfal, for making Con- 
vex-glaffes upon a Plain for all pra&icable lengths of Dia- 
meters of Spheres, without other diflies or concave Moulds 5 
we (hall, for the fatisfa&ion of fome of the Curious, that are 
not Mafters ot the Italian Tongue, and defire to know, what 
this way is, give it them in Englifh, thus 5 
To give a Spherical Figure to a Plain by a Ptain y (which at 
firft fight may feem a Paradox) by moving one Plain upon an- 
other by a circular Motion, proceed to this manner : Let the 
piece to which theGlafs to be wrought isfaftned, be adjnfted 
in the head of a Pole, which is to be of the length, the Semi- 
diameter of the Sphere of the Lens requireth $ and, upon the 
Stool or Form, where you intend to work, let there be put a 
J*/4/#ofIron or other Mettal, level to the Horizons and per- 
pendicularly over this Plain let the Pole be faften'd to the Ced- 
ing of the Room, if it be high enough 5 or to another fteddy 
faftning, lower than the Ceding, if need be > after this manner i 
About the head of the faid Pole let there be faften'd a Frame, 
made of two concentrkk rings or hoops , fo that the one be 
raovd within the other upon two Poles, and this other upon o- 
ther Poles, movable between twofmall arms fixt to theCeel- 
ing : which Frame you may imagine like that by which theMa- 
riaers Compafs is kept Horizontal, or that, which they ufe in 
Italy {ot carrying Oyl-lamps by night Horizontally : Off the fame 
may be done with a Ball moveable within two Circles fixed, and 
feften'd on the top of the faid Pole. All which will be better 
underftood by tht Figure*, in the firft of Which, the Lens isT, 
cemented to the Piece E, faften'd to the Pole % which pafles 
through the Center of the inner Circle B. moving upon the pi- 
vots I. H. {Fig. 2.) in the outer Circle A > and this isfaften'd 
m a Frame upon the pivots L M, in the arms C fixt iaa wall, 
Arable in the Ceding (as hath been faidj according to plea- 
