C *<J3 ) 
ufe ; which are now performed with much more Advan- 
tage by ihQ Algorithm or Numeral Figures now in ufe. 
After this Prefervation and Reftitution of thefe ancient 
Greek Authors, here follows a Collection of divers Let^ 
ters (relating to Mathematical Affairs) which have fot;- 
merly paflcd between Mr. OUenlurg, the Lord Broun^ 
ker^ Mr. Mentor, Monfieiir Lihitz\ and, more lately, 
between Dr. Wallis^ Mx^ndmt LihnitZy Monfieur Men- 
kenius, and (bme others) wherein may be feen by what 
Steps fome of the late Methods for the improving and 
promoting of Mathematicks have proceeded (and by 
whom truly made, and to whom juftly owing) as that 
of Dr. Wallis's Arithmetica hfinitorum ; which, by way 
of hduiliofi and Interpolation, (proper Methods of In- 
veftigationy but with Demonlirative Certainty^ hath gi« 
ven an In-let to many new Difcoveries, not formerly 
thought of, (Reducing 6^^^?w^/m<«/ Inquiries to purely 
Abftraded Arithmetical Confideration :) And that of 
Mr. Neutons Methodus Fluxiomm ; r^ed Monfieur Lil- 
nitz's Calcuks Differentialii ; with fome others. 
There is alfo an Account of the Bufinefs of Decipher^ 
ing (wherein Dr. Wallis bath been fo remarkable) with 
fome Specimens thereof. Which Art of the Do<5J:ors, 
Monfieur Lihnitz^ (a competent Judge) among many 
others, in a Letter dated the 14th. of March^ 1698^ 
which in this Colletftion is Epift. XXV. Pag. 688, calls 
thQ greateft Inflance that is known of tM Force and PenC' 
tratioH of humane Vnderftanding, 
With thefe follows a Letter of Dr. Wallis^ wherein he 
gives an Account of his Methods for teaching Perfcns 
Beaf and Dumh 10 fpeak, and to mdtx^diVid 2. La}?gu age i 
and thereby toexprefs their Minds by writing; and to 
underftand what other Improvements of Knoivledge may 
be obtained by reading : And for the correc^ting of Im- 
l^diments of Speech from Stutterif^g or Stammering, or 
otl m 
