^^^^^ 
An Exfrai^ of a Letter ofDr »J.WalIif^to lA.Heveimfiotn OxTordpccmU 
31. 1673. gramlatory for his Organographia^^nd particularly concerning 
Divifions'hy diagonal f.^ lately inier ted in Mr. fi^?<^i^x Animadvcrfiohs ou 
the Hrft part of the Machina Coelejils of the Honourable JohMvelim but 
Co faultily there printed, that it was thought ht, at the Authors defirc, 
in his Letter to the PubliOier, of Januar.^, 1 6jf, to be here done more 
corrededly. 
DVflicifaltem nomine^ (Clariffime Celehertimcqs Vir^) gratm T^ihi refe^ 
rendas haheosmeofcilice^&totm AcademU'-, propter duo dono data Or- 
ganographise tu£ n-uper edit£ Exemplariafilarijftmi Oldenburgii euro, tradi- 
ta. §^orHm alterum^mihi defiinatum^exofculatrn'-i alterum Infignijfimo Vice- 
Cancellario tradtdi^in Bodleiana Bihliothec'a (cum reliquii ftudiormn tuorum 
monumentU)reponendum, ^ui fm propterea atq^ Academic nomine grates re» 
fendi voluit:Mihiq\vkes fuas hae jn re permifit. 
Sed & efi cur^communi omniuth Liter atorum nomine/ehus pr<efertim Cceli- 
CPS addidiorum^reddam gratia^ i turn ob immenfos in tanto apparaiu fumptus e- 
rogatos^ tarn pretiofam conquirendo SupeUedilem Aftronomicam^ graphice hie 
defcriptam , turn oh indefejjos laboresjnfomnes nodes ^diefqsoccupatijjimosfix- 
lefiihus acqmrendi^ Ohfervationihw impenfos^quarum vim ingentem^hefaurum 
jHpraAurum& Margaritas pretiofum.^Erudito Orhi jam ante dederis^plura da- 
%HniS indies, Verkm non efi ut Jperem^me verbis square pojfe tua merita\qui ex 
privato penu fM,mptm plane Kegios erogafti > cnnfq\fufcepifii non. infeliciter^ 
Herculeis burner is(ne Atlanteis dicam)formidandum^ 
Operis partem maximam jam evolvr-ymiratus inibi iant£ moles Inflrum-en- 
iorum ingeniofum regimen\& Jubtilijfimam Divifionum adminiflrationemscum 
pari diligent id conjundamin Kegulis & Vioptris filicite curandis:Et quidem 
fi hoc deeffet/eliqum in cajfum cederet labor 5 quippe/xigum & vix evitabilrs 
in liegulis autVioptris error^ totum Infirumentum vitiaret^ omnefq^ i^ficeret 
Oh/ervationes, 
Sedfmgulis immorari non licet, , Vnum tamen efi quod attingam breviter s 
^empeJ)ivifiones per lineas Viagonales^ circulos in Limbo concentricos inter- 
fecantes, Hanc Dividendi methodum^jamdiu receftaM^ipfe retiness& quidem 
mjritV-iCirculofq^ hos concentricos^^qualihm intervals disjundos babes, ^od 
quamvis in exiguorum.aut etiam mediocrium^ Infirumentornm Limhis latiori" 
bm^ aliquid en-oris poffit indueere 5 in 'tuis tamen tant£ amplitudinis Infiru-- 
fnentis^cum limhis exigu£ latitudinis^(quod & ture^e mones^)nihil quivquam 
erit difcriminis quod in fenfu6 incurrere pojfit, 
Hac tamen occafione libet h ie fubjicere qncd ea de re jam olim ( circa An* 
' mum 16'^o^aut j6^i^)meditatu^ fimhatq-'i apud Adverfariameajamreperio, 
^Nempe\fiqu'vs vellet mifwrvs Infirumenti Limbum latiorem line'vs Viagonalibm 
fic dmdere\quibiis intervaliis oporteatconcentricos illos Circulos dij^onere^ut An-' 
gulos invicem equates defignarent iVdS circulorum cum tranfverfali interfe^fi" 
4ne > calculo "Irigonometrico determinare^ 
