ON TRIANGLES, &C. 23£ 



B A : A C, for. 2 ; therefore S A bifefls the angle B A N. 

 (Sunpfms EuclisL .6 A) ; alfo as B M : M A : : B C : C A ; 

 therefore C M bifects the angle A C B, Euc. 3.6 ; confequently 

 if two lines bil'ecl any two of the external angles of triangles, 

 and a third line bifeft the internal angle oppofite to thcfe an- 

 gles, thele Mrmft ftiall meet in one point by the laft propofition. 



Prop. 5. II B M be to M A as B P C to C"A ; and h O, O/be 

 perpendicular to BC and CA; kO is to O/'asBP-'Cto 

 C-A. 



Demonftratinn. As B M x O / : A M x O h : : B C : C A, 

 Cor. l. Prop. 2; and as B P C : A P C : : B M : M A by hypo- 

 thecs ; therefore as B P C x Of : A P C x O h : : B C : C A ; con- 

 sequently as Oh : Of: : B p — 'C : C p 'A. Q. E. D. 



III. 



A Communication on the life of Green Vitriol, or Sulphate of 

 Iron, as a Manure; and on the Efficacy of paring and burn- 

 ing depending, partly, on Oxide of Iron. By George 

 Pearson, M. D. Honorary Member of the Board of Agri- 

 culture, F. R. S. From a Communication made by him to the 

 Board, and inferted in the fourth Volume of their TrdnfaSkbns, 



(Concluded from page 214.) 



APPENDIX. 



1 HE following facts, lately difcovered by mod: refpedable 

 chemifts, appear to be worth adding to the preceding memoir, 

 as they ferve to fiiew that other falts, befides fulphate of iron 

 and certain earths, may be employed advantageoufly as 

 manures, although like iron they have been efteemed deleterious 

 to plants. 



1 . Afh.es of Pit Coal are a good Manure for Grafs. 



My much valued friend, the Rev. William Gregor, of The a/hes of pit 



Grampound, on examination of the allies of coal from Liver- coal aie ag° od 



r ' . manure tor graii, 



pool, found (hem to contain both fulphate of rnagnefia and 



fulphate of lime, efpecially the former, fait. I apprehend 



that thef'e allies alio contain oxide of iron, or perhaps fulphate 



of 



