MATTHEW YOUNG. 463 



statement is also affirmed by this pair. Then the memoir combines 

 the two pairs by the ordinary rule for concurrent testimony, and so 

 takes for the probability arising from the two pairs 



m^ -f i^nm + iff ' 

 Then the question is asked for what ratio of m to n this expres- 



sion is equal to , so that the force of the two pairs of wit- 



m -^ n ^ 



nesses may be equal to that of a single witness. The approximate 



value of — is said to be 4*86^ so that is about -^ . 



n m-\- n b 



859. In Vol. VII. of the Transactions of the Royal Irish 

 Academy there is a memoir by the Rev. Matthew Young, D.D. 

 S.F.T.c.D. and M.R.I.A., entitled On the force of Testimony in esta- 

 hlishing Facts contrai^y to Analogy. The date of publication of 

 the volume is 1800 ; the memoir was read February 3rd, 1798 : it 

 occupies pages 79 — 118 of the volume. 



The memoir is rather metaphysical than mathematical. Dr 

 Young may be said to adopt the modern method of estimating the 

 force of the testimony of concurrent witnesses ; in this method, 

 supposing the witnesses of equal credibility, we obtain a formula 

 coincidino^ with that in Art. 667. Dr Younof condemns as erroneous 

 the method which we noticed in Art. 91 ; he calls it "Dr Halley's 

 mode," but gives no authority for this designation. Dr Young 

 criticises two rules given by Waring on the subject ; in the first of 

 the two cases however it would not be difficult to explain and 

 defend Waring's rule. 



