I 
foeverj may be Ipeedily made: which Teems to him moil 
eafie 5 beeaufe, if it fucceeds, with one and the fame Tool 
may be ground an ObjeU Glafs of any length or breadth 
requisite , and that with very little or no trouble in fitting 
the Engin , and without much skill in the Grinder. He thinks 
it very exadb, beeaufe to the very lafl ftroke the Glafs does 
regulate and redfifie the Tool to its exadt Figure , and the 
longer or more the Tool and Glafs are wrought together, 
the more exadl will both of them be of the defired Figure. 
He affirms further, that the motions of the Glafs and Tool 
do fo crois each other,that there is not one point of eithers 
furface , but hath thoulands of crols motions thwarting it, 
fb that there can be no kind of Kings or Gutters made , ei- 
ther in the Tool or Glafs. 
5. _ A New Inflrument , by which the RefraUion of all kinds 
of Liquors may be exadlly meafured 3 thereby to give the 
Curious an opportunity of making Trials of that kind., to 
eiLablifh the Laws of RefraUion , to wit, whether the Sines 
the Angles of RefraU ion are refpeUively proportionable to 
the Sines of the Angles of Incidence : This Inftrument being 
very proper to examine very accurately, and with little 
frouble,and in fmall quantities ? the RefraUion of any Liquor, 
notonely for one inclination, but for all^ whereby he is en- 
abled to make accurate Tables. By the lame alfo he af- 
firms to have found it true, that what proportion the Sine of 
the Angle of the one inclination has to the Sine of its Angle 
of RefraUion , correfpondent to it , the fame proportion 
have all the other Sines of Inclination to their refpedfcive 
S ines of RefraUions. 
Laftly, this Author defpairs not that there may be found 
many Mechanical Inventions,to improve our Senfes of Hea- 
rmg^Smdlingpr afling^ Touchings well as we have improved 
that of Seeing by Optic f GlaJJes . 
London, Printed with Licence for John Marty n^ and James 
Alleftry^ Printers to the Royal Society. 
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