f 440 ) 
Ih A Defcription of HE LI OS CO? tS andfomt 
other InfirumentSj made by Robert Hook , Fellovf of 
the R. Society : London, printed for John Martyn 
at the Bell in 5f.Pauls Churchyard^ 1675. in 4^ 
Touching the Contents of this Book, as far as they relate 
to the Inftriiraents therein defcribed, I need fay nothing 
here: I fliall only touch upon fome paffagesin the Pojl-Jcript 
of ir , in which I find one of thefe our Trafls concerned. 
The faid Poftfcripc then takes the liberty of reflefting upon a 
paffage in A"^^/;»^. 112/^. of rhefe Traptfa^io^s^ viz. about the 
lnvef2Uon of appJjihg a Spring to the BalUnce of a, Watch , find- 
ing fauic with the fame for not having taken notice, ih^t this 
lnvfntionv0as jit ft found out hy an Englilh/»^;^ , and long fince 
fMJbedto the World ^ and complaining thereupon of unhand- 
pme proceedings. 
Now forafmnch as the former part of this accufation doth 
direftly concern the Author of thetranfa^Jions^ and the latter 
is fo ambiguoufly worded, as that it may be referr'd to the faid 
Author, as well as to the French Journal des Scavans^ it was 
thought fit to acquaint the Impartial and Candid Reader with 
the plain jTm^ of this matter. 
'Tis certain then, that the Defcriber of the Heliofcope, fome 
years a go, can fed tobeaftually made fome Watches of thiskind, 
yet without publifhing to the world a Defcription of it in 
print i but it is as certain, that none of rhofe Watches fuc- 
ceeded, nor that any thing was done fince to mend che In- 
vention, and to render it ufeful,that we know of, until Monfieur 
Iluf ens, who is alfo a Member of the Royal Society as well as he 
is of the Royal Jfcademy at f^m, fent hither a Letter dated 
30. 16'-^, acquainting us with an Invention of his of 
very exa& l ocket- watches , the nature and contrivance of 
which 
