58 ESSAYS AND OBSERVATIONS 



with the real ones, as to quantity. Many 

 inftances of this occur in Sir Ifaac New^ 

 tons writings, and in all mathematical philo- 

 fophy : fuch as the calcaktion of the 

 moon's irregularities ; of the tides ; of the 

 preceffion of the equinoxes j of the refi- 

 nance of fluids J and, in optics, his compu- 

 tation of the dimenfions of the rainbow ; 

 of the aberration of colours ; of the inter- 

 vals of th-e fits of reflexion and tranfmif- 

 fion ; and of the coloured rings reflected 

 by thick tTzn{p2LcentJ^eculums. 



- What further I have to offer concerning 

 light and colours, confifling chiefly of doubts, 

 difficulties or loofe conjectures, fhall be pro- 

 pofed under the form of queries. 



SECT. 



