4-0 Mifcellanea Curivfa. 



Irk. going out from the Sun, viz. in a Fluid of 

 a left Ratio .. In Oil o r Turpentine, the diftance 

 of this Iris from the Point oppofite to the 

 Sun, is obferved to be 8i°. 30'. whence the 

 curious Reader may find out the Roots , 

 6,80822-- and— 2, 981 31- - the Tangents of 

 the Iiefratfted Angles. Hence is computed the 

 Ratio of greater Inequality, as I to Q, 67995 - - 

 futh as is in Oil of Turpentine. But 'from 

 the greater Root comes forth the lejfer Ratio , 

 as t to o, 9540 nearly, fuch as would be in 

 a Fluid/ exhibiting a Secondary Iris of the 

 fame Diameter, but which (after the manner 

 of the Primary one) mould look towards the 

 Sun with the Red Colours. 



If .any one lias a mind to find thefe Roots 

 by a Geometrical Coaftru&io'n, any Parabola 

 being given, it is done with fo much eafe, 

 that I need not repeat what I have already 

 offered , upon that Plead Philofophical Tranf- 

 tittions, N. t 88. 



E ich of thefe Equations is deduced from 

 what has been faid before, and alfo from 

 the Rules for the Tangents of the Double 

 and Treble Arch ; the bare hint of which, 

 may be inftead of a Demonftration even to 

 th r e tbat are but meanly vers'd in thefe 

 things. 



This Difcourfe. being already in the Trefs, 

 there came to my hands (by the means of 4 

 Friend) a certain Book , whofe Title was 

 1 hanwanttadis Thanmafia , Printed at Norim- 

 herg 1699, under the Superintendency of Af. 

 Stirrmim. In which the skillful Author feems 

 to have laid together whatever is £0 be found 



