VOL. VI.] PHILOSOPHICAL TRANSACTIONS. 6l3 



IV. Francisci de le Boe Sylvii, M.D. et Prof. Oratio de Aftectus Epidemii, 

 An. 1669. Leidam depopulantis, Causis Naturalibus. Lugduni Batavorum^ 

 1670, in 12mo. 



In this discourse the author endeavours to prove, that the late wasting dis- 

 ease in the city of Leyden is to be imputed to the excessive heat, long continued 

 calms, want of rain, and the vapours of standing and muddy waters abounding 

 in that place, together with certain saline and noxious exhalations of the earth, 

 by the force of the sun propelled into the air, and there mingled with the 

 former. From which he considers, that all the various, and even the most 

 different and grievous symptoms, that were observed in the sick people at Leyden 

 may be rationally derived; adding his opinion of the cause why rich and deli- 

 cate persons were first of all and sooner attacked and destroyed by that disease, 

 than those of the poorer and hardier sort of people ; though these latter fell in 

 greater numbers about the end of this sickness, than the former. 



In the discourse about the ill effects of a tainted air upon human bodies, he 

 takes occasion to insinuate, that as it is difficult to prove, so it is hard to deny, 

 that some part of the inspired air is also commixed with the saliva, and being 

 (together with other humours, falling from the brain and its glandules and the 

 glandulous tunicles,) derived to the mouth and throat, and so swallowed together 

 with the same, causes in the stomach and small guts some alterations in the 

 humours there found or meeting together. But as he thinks this not improba- 

 ble, so he judges that there are yet required many accurate observations to clear 

 up and establish so obscure a doctrine. 



V. Hypothesis Physica nova, sive Theoria Motus Concreti, una cum Theoria 

 Motus Abstracti. Auth. Gothofredo Guilielmo Leibnitio,* J.V.D. et Con- 

 siliario Moguntino. Londini, 1671, in 12mo. 



* Godfrey William Leibnitz, a philosopher and mathematician of the first rank, was bom i6a6 

 at Leipsic in Germany, his fatlier being professor of moral philosophy in that university. He had an 

 early predilection for mathematics and philosophy, and began the study of the sciences at 15 years of 

 age. Indeed his reading and course of study were extensive and universal, but that of the law was 

 pursued as a professional one, in which faculty he was admitted bachelor in l665 at Jena, and doctor 

 the year following at Altorf. In l673 he visited Paris, where he cultivated the acquaintance of the 

 literati, and improved himself by the study of the mathematical writings of Pascal, St. Vincent, 

 Huygens, &c. In l673 he visited England, and became acquainted with the learned men of the 

 Royal Society, particularly Mr. John Collins, from whom it seems Leibnitz received some hints of 

 the method of fluxions, which had been invented by Newton in l664 or l665. The same year he 

 returned to France, where he resided till I676, when he again passed through England and Holland, 

 in his journey to Hanover, where he proposed to settle. In 1700 he was admitted member of the 

 Royal Academy of Sciences at Paris. The same year, by his advice, was founded an academy at 

 Berlin, of which he was appointed perpetual preiident. He also projected an academy of the same 



