f2045 ) 
remains unmoved. Wherefore in this Tranfparent fubftance^ 
the Image which appears fixt^ may proceed according to the 
ordinary Lawsof t>5^^/Refraaion 5 but that, which moveth, 
and is carried about according to the motion of the Diapha- 
nous Body, while the Objeft remains un-ftirr'd, flieweth an 
Vn ufiat kind of Refraftion, hitherto un-obfcrved b^Diof- 
iricians. 
Hence, that I might examine the nature and difference of ^ 
both, I putj upon fom^Objeftj as the point Ajthe Pri(rne of V 
my Double- refrafting Chry ftal Nj P, R, Q., T, B, S , and ) 
the Eye M, being perpendicularly pofited over the uppe^ - 
plain of the Prifme N, I noted ^ whether there 
was any Refraftion of the point A, (for the njiid Laws cjf i 
Refraftion teach^ that there i$ none. ) But the Perpendicu^ 4 
