fee the Moony bat as if we were a i oo, or at leaft^ <ro. leagues di- 
ftant from her without a Glafs. He here wiftiesjthat thofe , 
that promife to make us fee Animals and Plmnts in the Moon , 
had thought on what our naked Eyes can make us difcern of 
fuch ObjeiitSj only at lo or 1 2 leagues diftancc. 
But this he would not haveunderftood as a difcouragement 
from fearching with all care and earneftnefs after the means of 
making long Tdejcopes^ or of facilitating the working thereof ^ 
but only as an Advertifement to thofe, who light upon the The« 
ery of any Engine^ not to expofe it prefently as poflible and ufe- 
ful, before they have tried it, or if it have fucceeded in fmall ^ 
not to endeavour to perfuade, that it will alio fucceed in great. 
As it may happen Qaub he ) that the Engin of Mr. Hoo\ may ^ 
by uling all neceflary precautions.fucceed in the makingof ^j^- 
Glajpf^qr/mall Optick-GlalTeSj but noc in making great ones ; 
as wefee,thataninftrument compofed of two Rulers, where- 
with are traced Portions of Circles ^ fucceeds well enough in 
frnaB^\xt when there is no more than half a Line* a quarter of a 
Line^ or Icfs convexityjit will be no longer juft at alljas he tells 
us to have made the proof of it inCircles drawn by the means of 
one of thefe Inftruments, made by one of the beft Workmen 
in his time, who, whilft he Hved, efl:eemcd them above price, 
although they be not jufl 5 as others and my Mi (faith he) have 
bytryal found, when we endeavoured to make M^^x^Wj by theit 
means, & as thofe^who by the Hke Inftrument laboured to trace 
portions of Circles of Ho or 100 foot, &c. Diameter, can attefl:. 
But, notwithftandiog all this, he hath thought upon two or 
three things, which he thinks may remedy (ome inconvenient 
cies of Mr. Ho&^his Turn. The firft is, to invert the Glafs, and 
to put it under the7(?>2g,that fo not only theGlafs may be placed 
more H orient aiy.'^ud. not Aide upon theCiem^w^,but that the Sand 
aHo,and the Putty may ftay upon the Glafs. 
The other is, that there muft be two Poppetheads^ into which 
the Mandril muft pafs, where the J{ing is to be faftned 5 and the 
Mandril muft beperfedlly Cylindrical, that fo it may advance 
upon the Glafs as it wears away by the means of its weight 5 or 
by the means of a fpring, preffing it, without wrigling from one 
place to another^ as it would prefcndy happen in the fafliion , 
I as 
