1802.] 
in the sputinctrina! ory ale aad calcu- 
lus, I fhould approve of your adding’them 
as an Appendix ; your/name would then 
grace my work infinitely, and you would 
therein be kind above meafure to Mr. 
Tooke, who undertakes the work, and 
would hereby fecure its fale. Pray, dear 
Sir; let me intreat this favour from you, 
and I do affure you, I'll make it my per- 
petual indeavour to return the obligation. 
If your next letter give me any hopes of 
this requeft, I faall be the moft-rejoye’d 
man in the world; but, if you are filent 
therein, I fhall be the. moft dejected, as | 
thinking you look on my work as not de- 
ferving ‘the ornaments you could give it. 
I am your moft humble fervant, 
WILL. MOLYNEAUX. 
P. S. We have no news from Ireland, but 
expe& it every hour. fam credibly inform- 
ed, that all the Irifh horfe want thoes, and 
alfo their foot, infomuch, that a’ pair'of thoes 
are fold in Limerick at 40s. (brafs), a bottle 
‘of wine 12s. and’a pot of ale 35.—’tis certain 
their wants are very prefling. 
Mr. Molyneaux, the writer of the above 
_letter, is perhaps better known as the friend 
and correfpondent of Mr. John Locke than as 
a mathematician, In 1689, among great 
numbers of other Proteftants, he withdrew 
from the difturbances in his native country 
({reland), owing to the feverity of Tyrcon- 
nel’s government; and, after a fhort ftay at 
London, fettled, with his family, at Chefter; 
here he employed himfelf in arranging the 
materials he had fome time before prepared 
for his Treatife on Dioptrics, in which he was 
afified by Flamftead. In Auguit, 1690, he 
went to London to put it to the prefs, where 
the theets were revifed by Dr. Halley, who, 
at the author’s requeft (as appears by the 
above letter) gave leave for printing, in the 
Appendix, his celebrated Theorem for finding 
the Foci of Optic- glafies, The. book was 
-publifhed in 1692, in quarto, under the title 
of Dioptrica Nova ;—a 'Treatife of Dioptrics, 
in two parts, wherein the various effeéts and 
‘appearances of {pherical glafies, both convex 
and concave, fingle- and. combined, in te- 
lefcopes and microfcopes, together with their 
ufefulnefs in feveral concerns of human life, 
are explained. 
He called it ** Dioptrica Nova,” becanfe it 
was almoft wholly new, very little being bor- 
rowed from other writers, and becaufe it was 
the firft book publifhed on that yee in the 
Englith language. 
It does not contain any of the more cu- 
rious fpeculations in optics, that, being fo- 
reign to his defign, but feveral of the moft 
generally vfeful propofitions are demonftrated 
‘in a clear and ealy manner. The fecond part 
is very entertaining, efpecially in the hiftory 
which he gives of the feveral optical inftru- 
nents, and the difcoveries made by them, In 
Original Letters, by Mr, Molyneause. 
» Human Underftanding.” 
S83 
the dedieacibn of the work (which was ad 
drefled tothe’ Royal Society}, he takes non 
tice,among the improvements that had then re~ 
ceatlybeen made in philofophy,of the advances 
that had alfo been made in logic, «* by the 
imcomparable John Locke, in his Effay.on 
This drew a letter 
of thanks from Mr. Locke, that foon grew 
into an intimate friendfhip, and a mutual core 
refpondence fubfifted between them till the 
time of Mr, Molyneux’s death, which hap. 
pened OGober 11, 1698. 
Befides the work above-mentioned, he was 
author of 
1. §© Scicthericurm Telefcopicum,” containing 
the defcription and: ufe of a telefcopic-dial, 
Dublin, 1686.—See Philos. Trans No. 184. - 
2. ** The Cafe of Ireland-ftated, in Rela» 
tion to its being bound by Acts of Parliament 
made in England.” In this work, he was 
greatly afhited. by Mr, Locke. 
The following papers in the Philos. Trans. 
were alfo written by him. 
re Why four Convex-glaffes i ina Hatin 
thew Objeéts ere@, No. 53. 
2. Defcription of Lough Neagh, in Ireland, 
No. 158, ° : 
3, On the Connaught Worm, No. 168. 
4. Deicription of a New Ee eet 
No. 172. 
5- On the Caufe of Winds, ahi the Change 
of Weather, dec. No, 177. 
6. Why Bodies diflolved fui in Men- 
firua specninadly lighter than: themfelvés, 
Mo, 18t. 
. On the mitten. No. 134. 
g. Obfervations, of Eclipfés, No. 164,—«. 
185. 
g. Why Celeftial Objeéts appear greatelt 
near the horizon, No. 137. ~~ 
~to. On the Errors of Surveyors, arifing 
from the Variation of ge Magnetic-needle, 
No. 239. . FR: S. 
ERRATUM.—In Halley’s Letter to Flam- 
ftead, page 326, lines fecond and third, of the 
agazine for November, read “ the diftance 
of cor WY from [pica TQ 45° 51° 2",” &ee 
& 
ORIGINAL LETTER of the late SIR GEORGE 
»SAVILE. 
MADAM, Rufford, Fan. 27, 37576 
“8 NHE interfermg in the private con- 
cerns of a family feems, in general, 
very much to want an apology. I have 
no other to make for doing it, than a per- 
fuafion that I am doing right, and a belief 
that what Iam about to fay may be of 
fervice.to one, whom, I doubt not, you 
retain a real’ affection for, notwithitanding 
one capital breach of duty. 
You eafily guels, I mean your daughter 
at Egmonion. 
The final rent T have a demand on ber 
8 ’ hufband 
~ 
