On the Measure of the Force of Testimony in cases of Legal 

 Evidence. By John Tozer, Esq., M.A., Barrister-at-Law, Fellow 

 of Gonville and Caius College. 



The ohject of this paper is to show that the assumptions made by 

 some English legal authorities on this subject, in opposition to the 

 principles established by scientific processes, are not justified. 



The views more particularly dissented from, as extracted from a 

 work of high legal authority, are thus enunciated : — 



" The notions of those who have supposed that mere moral pro- 

 babilities or relations could ever be represented by numbers or space, 

 and thus be subjected to arithmetical analysis, cannot but be regarded 

 as visionary and chimerical. 



" Whenever the probability is of a definite and limited nature 

 (whether in the proportion of one hundred to one or of one thousand 

 to one, is immaterial), it cannot be safely made the ground of con- 

 viction ; for to act upon it in any case would be to decide, that for 

 the sake of convicting many criminals the life of one innocent man 

 might be sacrificed. 



" The distinction between evidence of a conclusive tendency which 

 is sufficient for the purpose, and that which is inconclusive, appears 

 to be this : the latter is limited and concluded by some degree or 

 other of finite probability beyond which it cannot go ; the former, 

 though not demonstrative, is attended with a degree of probability 

 of an indefinite and unlimited nature." 



The method pursued is that of investigating algebraic expressions 

 for the probabilities that the allegations made in a case which ac- 

 tually occurred, the trial of a female for murder, are true ; and thence 

 deducing an expression for the probability of the truth of the charge, 

 in passing from the symbolical to the numerical expression, the num- 

 bers employed are not the actual values of the symbols but their 

 limiting values ; the resulting number is therefore a fraction which 

 is not less than the value of the probability of the truth of the prin- 

 cipal allegation, this being what in practice is required. 



The conclusion arrived at is, that the mode of estimating the force 

 of evidence employed in a court is a process which algebraic inves- 

 tigation analyses, and of which it explains the theory, and an ap- 

 proximation to a result which is obtained with accuracy by assigning 

 numerical values to the algebraic symbols : a clear conception of the 

 nature of the practical process, it is conceived, must render its appli- 

 cation more accurate, and to the extent of affording this the investi- 

 gation is deemed to be of practical utility. 



December 11, 1843. 



On the Motion of Glaciers. By William Hopkins, M.A., F.R.S., 

 Fellow of the Society (Second Memoir). 



In a previous memoir Mr. Hopkins had given the details of cer- 

 tain experiments, by which it was proved that ice will descend with 



