^rcporcujj on which occafion he ventures to eypbin almoft 
the whole Philolophy of Magneuc\5, Then he difcufieth 
the QucftioD, Whether the dijSDfion of Light be Injlantanecus^ 
and coiicludeth it in the JSegative ^ though the DuiaticD of it 
be imperceptible. This done , he examines the nature of 
Reflexion and Refraftion, and fee ms to acknowledge , that, 
fuppofing Light to be a Subfiaficc very fluid and veryfubtile, 
an account may eaiily be given 3 why it is reflected and re- 
traced , and why it obferves fuch Laws in its reflexion and 
refraftion, as really it doth. 
Further^ he difcourfeth of Colours.^ and confiders , How 
Light is changed into Colour, fometimes by Reflexion alone, 
lometimes by Refraction alope 5 fometimes without either 
and without the change of the Medium 3 vid, by DijfraUion, 
He explains alfo. How Light by the fole intrinfick modifica- 
tion of it felf, paflTeth fometimes into a colour that is com- 
monly called 4p/^^r^«^: Where he declareth, that the reafoiij 
why Light pafleth into an Apparent colour , is notfome de- 
terminate Anglej at which the rays amongfl: themfelves are 
inclined^ but that that Colour is produced by the intenfion 
and deiifiiy of Light. He teaches alfo. That to the Vifion 
of things permanently colour'd 5 there are not required any 
intentional fpecies^ tranfmitted from them, and contradifl:icft 
to Light 5 but that the Lights which is diffufed 5 oratleafl:re- 
fled:ed from things colour'd^ is fufBcient ; yet with fuch a Mo» 
dificationj as is to be found in Light apparently coloured : Oo 
which occafion many particulars are delrvered concerning 
J{eflixV\^\Qn ^ together with an Explication of that ^£re^ 
How the Place of the thing feen is perceived P <6?^r. To all 
which is added 5 that the Modification of Light, by which it 
is both permanently^ and ( as they fpeak ) apparently coloured, 
or made fenfible under the reprefenration oi Colour, may not 
improbably be faid to be a determinate and moft finely fur^ 
row'd Undulation of the fame, and a kind of tremulous dif- 
fufion, with a certain very fubtle floating ^ whereby it doth, 
inapeculiar way of application, afFedt the Organ of Vifion: 
Which is illuftrated and confirmed by what is by Philofophers 
Ff f f 2 taught 
