VOL. XV.] PHILOSOPHICAL TRANSACTIONS. 249 



by night, in performing arithmetical operations in great numbers, better than 

 by day he could have done; and even by day we may better do it with our eyes 

 shut, than open. And at their next meeting, March 31, J 685, he gave this 

 further account of it. Having had the curiosity to try how far the strength of 

 memory would suffice, to perform some arithmetical operations, as multiplica- 

 tion, division, extraction of roots, &c. without the assistance of pen and ink, 

 or any thing equivalent ; and finding it to succeed well, for instance, in ex- 

 tracting the square root, from numbers of 8, 10, 12, or more places; he then 

 tried it with success in numbers of 20, 30, or 40 places ; particularly in the 

 square root of the number 3, which he found to be 1,73205,08075,68877.29353; 

 also, at the request of a foreigner, he took another number at random, consist- 

 ing of 53 places of figures, and in the dark of the night extracted its root to 

 27 places, by the usual process ; both which he retained in his mind, till he 

 afterwards wrote them down by day light. By which he was sufficiently satis- 

 fied, that a tolerably good memory, fixed with close attention, is capable of 

 being charged with more than at first may be imagined. 



On a large Slone voided by Urine. By Dr. Wallis. N° 178, p. 1271. 



A model, or pattern of a stone, which came from the bladder of Mrs. E. V. 

 of Wallingford, at the age of 63 years, Aug. 7> l685, was communicated to 

 the society of Oxford. The compass of it was 5-i- inches ; its length A\ inches, 

 and weight 3 ounces avoird. This stone was drawn out by the hand, with- 

 out instruments. Since its discharge, she has been troubled with urinae 

 incontinentia. 



On the JVurtemburg Siphon. By Dr. Salomon Reisel, Chief Physician to the 

 Duke of IVurtemburg. Abridged from the Latin. N° 178, p. 1272. 



That I may not long disappoint the wishes of the Royal Society, I must 

 confess that the siphon described by the excellent Dr. Papin, is the very same 

 as the Wurtemberg siphon, which I proposed, also made with a recurvation of 

 the lower ends. Nor is there any other mystery at the top, as the inventor 

 has described, than that it must be filled with a funnel, as without being so 

 filled, it cannot run away. This shall soon be confirmed through the press, as 

 it would be too tedious to set down all the particulars in this place. 



A full Description, with the Use of the new Contrivance for raising fPater, 

 propounded in the Philos. Trans. N" 1 73. By Dr. Papin, F. R. S. N" J 78, 

 p. 1274. 

 In pi. 8, fig. 5, A A is the great tumbler, which must have some small hole 



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