ExSrait of d Letter from Mr. Butterfield MathemAtique In- 
Jlrument-maker to the French King , about the making of 
Microfcofes with very [mall and Jingle Gla[fes : and offime 
ther Injlruments, 
I Doubt not but y oil may be as bu(ie at London we are 
here in making of Microfcopes of the manner lately brought 
out of Ihllitndhy Mr. Huigens, whereof I have of feveral 
fafliions ready made. I have tried feveral ways for the making 
o( Glafles of the bignefs of a great Pins head and lefs ; as in the 
flame of a Tallow- candle, and of one of Wax, But the beft 
way of all I have yet found, to mikeihem clear and without 
fpecks, is with the flame of Spirit of Wine well reflified, and 
burned in a Lamp, Inftead of Cotton I make ufe of very 
fmall filver wire doubled up and down like a skein of thred ; 
, which being wet Willy the Spirit of Wine , and made to burn ' 
in the Lamp, giveth through the veril of the Lamp a very ar- 
dent flame* Then take your beaten Glafs, being firft waflied 
very clean , upon the point of a Silver needle filed very fmaH, 
and wee with fpittle. Hold it thus in the flame till it be quite 
round, and no longer for fear of burning it, and if the fide of 
the Glafs next the needle be not melted, you may put it off 
and take it up with the needle on the round fide, prefeoting the 
rough fide to the flame till it be every where very round and 
fiiiootb, then wipe and rub one or feveral of them together 
withf fcleatber, which makes them much the better. Theq^ 
put them bet ween two pieces of thin bra fs, the Apertures ve- 
ry round and without bur, and that towards the eye fo big al- 
moftas the diameter of the Glafs: and fa placed in a Frame 
with theobjeft conveniently for obfervation. 
I publiihed laft year in rhe Journal de Scavans a trial of mine 
Invention with a Tube with GlaflTes and a Thred banging be- 
t\^een four points, with a weight in a Box fo contrived, thatar 
foon as the Inftrument is fet down, you have your point ofHo^ 
rzon with a great deal of exaftnefs ♦ It hath been fo well ap- 
proved of, that the River which the King maketh to come 
I wenty Leagues pfF to FariSyis conduSed by it,. 
At 
