A: Series of QnetQ^s propounded by Mr. Ifaac NewtoDj tQ he de- 
termindhy Experiments , pBpively and direHly concluding hu 
new Theory of Light and Colours '-^ and hre recommended to the 
InduBry of the Lovers of Experimental Thikfophy, as they rvere 
gen mujly imparted to the Publtjher in a Letter ofthefatd Mr, 
Newtoilso/^ July B. i672» 
IN the meao while give me leavCj Sir^ to infinuatejthat I can- 
not think it effe<aual for deteraiiniog triachj to esamin the 
feveral waies by which ^FhMiomena may be explained, unlefs 
where there can be a perfed enumeration of all thole waies. 
You know5the properMethod ^ox inquiring after the properties 
of things isjto dedues them from Experiments^And 1 told you^ 
that the Theory^which 1 propounded, was evinced to mCj not 
by inferring 'tis thus becaufe not otherwife, that is 5 not by 
deducing it.only from'a confutation of contrary fuppofitionSj 
but by deriving it from Experiments concluding pofitively 
and diredly* The way therefore to examin it is^ by confi- 
deringj whether the Experiments which I propound do prove 
thofc parts of the Theory^ to which they are applyed j or by 
profecuting other Experiments which the Theory may fug- 
geft for its examination. And this I would have done in a due 
Method 5 the Laws of RefraBion being throughly inquired in- 
to and determined before the nature of Colours be taken into 
confideration. It may not be amifs to proceed according to 
the Series of thefe §^£ries 5 which I could wifli were determi^ 
ned by the Event of proper Experiments • declared by thofe 
that may have the curiofity to examin them. 
I. Whether rays, that are ^/i-^e incident on the fame M^^i^ 
um^ have unequal re(rzdi\Qns ^ and how'great are the inequa- 
lities of their refradiions at any incidence? 
s. What is the Law according to which each ray is more 
er lefi refradled j whether it be that the fame ray is ever re- 
frafted according to the fame of the fines of incidence 
and refraition ; and divers rayf^according to divers ratio's'.^ ot 
that therefradtion of each ray is greater or le(s without any 
certain rule ? That is ^ whether each ray have a certain de* 
gree of refraogibility according to which its refrad:iou is per«» 
iormed j or is refraded without that regularity f 
3^ Where- 
