292 *' Dr. Price and his Followers." 



or thread ; and t the thickness of the wood into which it is 

 forced, — all in inches ; f being the force in pounds to extract 

 the same. 



We may from the above experiments observe the approxi- 

 mation to perfection in the art of screw-making : for had the 

 screw been greater in diameter, there would have been a waste 

 of material ; or had it been less, it would have been not suffi- 

 ciently strong, which may be proved as follows : 



The cohesion of wrought iron has been found from a num- 

 ber of experiments to be about 43,000 pounds per cylindrical 

 inch ; and as the smallest diameter of screw used in my experi- 

 ments was "15, it would have been torn asunder by a force of 

 about 968 pounds; or if the hard wood had been 5-8ths of an 

 inch thick, into which it had been screwed, the screw would 

 have been broken, instead of forcing its passage out of the 

 wood. B. Bevan. 



XLIX. " Dr. Price and his Followers" (See Phil. Trans, 

 for 1826. Part iii. p. 297.) 



T KNOW not, neither am I anxious to learn, for whom this 

 -■• civU appellation is intended. If it merely refers to those 

 theorems of Dr. Price which have been the subject of Dr. 

 Young's animadversions in his late communication to the Royal 

 Society, I should think it impossible that any person acquainted 

 with the subject, would have the least difficulty in determining 

 which of the two Doctors he should prefer to follow on this 

 occasion. 



In the 66th volume of the Philosophical Transactions, Dr. 

 Price gave sundry theorems for determining the values of 

 annuities when the payments are made at shorter intervals than 

 one year, and for that purpose proceeded on the same princi- 

 ples in investigating the values of the different payments with 

 those universally adopted in regard to the values of such pay- 

 ments when they are made annually; for if 1/. increased by 

 its interest for a year, or 1 + r, be the amount of 1/. in a year, 

 1/. increased by its interest for a shorter term will be its amount 

 in that term. Supposing therefore such term to be '/ath part 



of a year, — will be the interest, and consequently l-\ will 



be the amount. The converse therefore of these expressions 



or and will be the present value of 1/. to be re- 



* + '■ i+v 



ceived at the end of a year, or at the end of —th part of a year. 



—The 



