I 



VOL. XLIX.] PHILOSOPHICAL TRANSACTIONS. 579 



recorded, this inscription might have been erected in compliment to him under 

 that character. 



A Catalogue of the Fifty Plants from Chelsea Garden, presented to the Royal 

 Society, by the Company of Apothecaries for the Year 1745, Pursuant to the 

 Direction of Sir Hans Sloane, Bart. &c. p. 78. 



[This is the 33d presentation of this kind, completing to the number of l650 

 different plants.] 



XIX. On the Advantage of taking the Mean of a Number of Observations, in 



Practical Astronomy. By T. Simpson, F. R. S. p. 82. 



It is well known that the method practised by astronomers, to diminish the 

 errors arising from the imperfections of instruments, and of the organs of sense, 

 by taking the mean of several observations, has not been so generally received, 

 but that some persons of note have publicly maintained, that one single obser- 

 vation, taken with due care, was as much to be relied on, as the mean of a great 

 number. As this appeared to be a matter of much importance, Mr. S. was in- 

 clined to try whether, by the application of mathematical principles, it might 

 not receive some new light ; whence the utility and advantage of the method in 

 practice might appear with a greater degree of evidence. 



But the rest of this paper will be better consulted in Mr. Simpson's Miscel- 

 laneous Tracts, published in 1757, where the paper is much improved. From a 

 particular example which Mr. S. calculates, he infers that the chance, for an 

 error exceeding 2 seconds, is not -^ part so great from the mean of 6, as from 

 one single observation. And it will be found, in the same manner, that the 

 chance for an error exceeding 3 seconds, will not be t-bVo P^rt so great from the 

 mean of 6, as from one single observation. On the whole of which it appears, 

 that the taking of the mean of a number of observations, greatly diminishes the 

 chances for all the smaller errors, and cuts off" almost all possibility of any great 

 ones : which last consideration alone seems sufficient to recommend the use of 

 the method, not only to astronomers, but to all others concerned in making ex- 

 periments of any kind, to which the above reasoning is equally applicable. And 

 the more observations or experiments there are made, the less will the conclusion 

 be liable to err, provided they admit of being repeated under the same circum- 

 stances. 



XX. Of the Success of Agaric, and the Fungus Finosus, in Amputations. By 



Mr. James Ford, Surgeon, of Bristol, p. 93. 



Mr. F. here gives an account of 2 cases of amputation, in which the agaric 



was successfully employed as a styptic. 



4 £ 2 



