( 4010 ) 
1iaht, at an hundred foot diftaece, and that at an hundred 
and twenty foot diftance I could difcern fome oi the words. 
When I made this tryal^ its Aperture ^defined next the Eye) 
was equivalent to more than an inch and a third part of the 
Obje£t-metalU This may be of fome ufe to thole that (ball 
endeavour any thing in Refiexions j for hereby they will in 
fome raeafure be enabled to judge of the goodnefs of th^ir 
loftruments, Sec- 
N. B. The Reader may exped: ill the next Month another 
Letter^ which came fome what coa late co be here inferted 5 
containing a Table^ Calculated by the fame Mx.TSlewten^ a* 
bout the feveral Apertures d^tidi Charges anlwering the feveral 
Length of thefe Telefcopes. 
EM TO ME 
Binaet .Methodi * Tangentium Do(9:oris Jobannis Wallijii 
Geom. Prof* Saviliani Oxonis 5 alias fufius & explicatius ab 
ipfo traditse^ hie vero ob anguftiam loci compendifaftse : 
Inquarum Schematiimis fi forfanliterce quasdam redundas 
verintj illas ad ea pertinere ceqfend^ funt, quse in ampliori 
ejufdem Seripto continentur^ hie vero diStde caufaomit- 
tantur. 
Abes hie {Clarijfime vir) eorum fumrmm {JiriBim traditam) 
qu(e fufms fmpferam, mem de Tangent ibus Methodos 
fpeBantia ^ duos potfjjimum quibus priejertim utor^ alteram in Spe' 
eiebusy alteram in Lineis j utramque generaliformh facile explica* 
Friorem adhibeo Con.$tdL,^to^.i:^,^o^'^6^^6ySt^.^ pajfimalibK 
^mhceceji, 
ExpoJitaburvdja^Quta Vatzhoh, fig. 4.) q^mm in tt tangat 
^^F, diametrd VD Joccurrensin F^ ordinatim applicentur ^tV^ 6 
BOT curvminO M tangentiinToccurrens. Fonatur autemFtf> = h^ 
FA::^V:, FF^(y adedque DJ-v DF^^^as 
0 (propter fmli^triaf^la) FFMF : t F^^DTzz^^h. 
Item, ptangens (it ultra cur vam^ DO i fi citra dT< 
DO : JSIempe^ DT^BO fi intelligatur D in fed^ ft\xtraV, 
dT vd DO my or prout tangens efi^ ultra citrave cur v am. 
