450 PHILOSOPHICAL TRANSACTIONS. [aNNO 1754.. 



sibly live, supposed to be due at the end of each of ] , 2, 3, &c. years ; it will 

 follow that their amount, or the difference between the values of the 1 annuities, 

 will be equal to the quotient found by dividing the value of an anuity of ll. 

 certain, for as many years as the annuitant can possibly live, by twice that num- 

 ber of years : and therefore, if to the value of an annuity for life, of the first 

 kind, we add the quotient so found, the sum will be the value of an annuity of 

 the second kind, for the same life. 



When Mr. D. had thus investigated the value of this annuity, he compared 

 the result with that M. de Moivre had deduced from fluxions, and published in 

 N" 473 of the Phil. Trans.; and found that they agree to more than a sufficient 

 exactness, for computations of this nature. He then annexes this comparison. 



The probability of any order of survivorship, that can happen among 3 per- 

 sons, and consequently that of one person's surviving 2 others, may likewise be 

 investigated on similar principles, without the assistance of fluxions ; but as this 

 problem admits of 6 cases, and the algebraic process is of a length too great for 

 the designed limits of this essay, Mr. D. omits it. 



LXITI. On the Pheasant of Pennsylvania,* and the Otis Minor. By Mr. George 



Edwards. •\- p. 499. 

 What is called the pheasant in Pennsylvania, and other provinces of North 

 America, belongs to that genus of birds, which in England we call heathcocks, 



* This bird is the Tetrao Umbellm of Linneus, and is extremely well figured iti the 1st volume of 

 Edwards's Gleanings of Natural History, pi. 248. 



t From the Memoirs of his Life, published in 1776, it appears that Mr. George Edwards was bom at 

 Stratford, a hamlet belonging to Westham in Essex, on the 3d of April 1694. He passed some of his 

 early years under the tuition of a clergyman named Hewit, who was then master of a public school 

 at Layton-Stone, a few miles distant from the village where he was born. After quitting the school 

 he was placed with another minister of the established church at Brentwood; and being designed by 

 his parents for business, was put apprentice to a tradesman in Fenchurch-street. 



On the expiration however of his apprenticeship, he declined entering into business, and conceived 

 a design of travelling, in order to improve his taste, and enlarge his mind. He first visited Holland 

 and afterwards Norway, and having gratified his curiosity with the view of these regions, returned 

 and passed some time in his native place. He then went to France, where, on visiting Versailles 

 he experienced great disappointment at finding that the Menagerie, once so celebrated, had at that 

 time no living creature in it, having been totally neglected since the death of Louis the 14th. On 

 his return to England Mr. Edwards closely pursued his favourite study of Natural History, employing 

 himself in making drawings of such animals as happened to fall under his notice; and the accuracy 

 and elegance of his delineations was such as to make them highly interesting to those who cultivated 

 similar pursuits. He therefore was induced to turn to advantage what was begun only for amuse- 

 ment, and obtained a sufficient subsistence by the sale of his drawings. In December 1733, by the 

 recommendation of Sir Hans Sloane, he was chosen librarian of the College of Physicians ; an office 

 peculiarly suited to his taste, as it gave him constant access to many works on the subject of Natural 

 History, which he might otherwise have found a difficulty of inspecting. In 1743 the first volume 



