On a General Method in the Theory of Probabilities. 431 

 Fig. 3. 



By the use of this little contrivance, perfect adjustments which 

 would otherwise require a very considerable time, may be made 

 in a few seconds. 



LIV. On a General Method in the Theory of Probabilities. By 

 George Boole, LL.D., Professor of Mathematics in Queen's 

 College, Cork"^. 



Preliminary Statement of Principles. 



1. nnHE class of questions which I propose to consider here 

 A is that of which the data consist of — 



1 st. Probabilities of events, or of combinations of events, capable 

 of being expressed by the signs of ordinary language ; 



2nd. Absolute connexions or conditions among events capable 

 of similar expression ; 



and of which the qusesitum or element sought is also the pro- 

 bability of some event or combination of events whose expression 

 is known. Thus the elements of the question considered in my 

 paper (On the Conditions by which the Solutions of Questions 



* Communicated by the Author. 



