ON INSTRUMENTS FROM ITALY. 135 



vando" (By trying, and trying again). The members present at this 

 celebrated meeting were : Vincenzo Viviani, Alfonso Borelli, Carlo 

 Rinaldini, Alessandro Marsili, the brothers Paolo and Candido del 

 Buono, Antonio Oliva, Lorenzo Magalotti, Francesco Redi, and Carlo 

 Dati. Among the Italian correspondents, Ricci, Cassini, Montanari, 

 Rossetti, and Falconieri must be mentioned ; and among foreigners, 

 Stenone, Tevenot, and Fabbri. 



It is not my intention to speak individually of each of these 

 academicians ; the limited time at my disposal would not permit of 

 it ; nevertheless, before speaking of the labours of the Academy, I 

 cannot but add a few words more respecting one or two of them. 

 And above all I must mention Viviani, Galileo's only disciple, a subtle 

 and industrious academician, to whom we are indebted for many 

 experiments which led the way to the discovery of the theory of undu- 

 lations, the general idea of which, he even at that time, suspected. 

 We owe him likewise a barometer, without a small well (pozzetto) ; 

 experiments on capillary phenomena, independent of pressure ; the pro- 

 position for finding the weight of ice compared with that of water ; the 

 experiments on the swim-bladder of fishes ; but, above all, the machine 

 for making a great vacuum, to which primitive shape of a pneumatic 

 instrument we have at present returned, giving it the name of mer- 

 curial ; and many persons dispute the invention of such a machine, 

 forgetting all the while that the first instrument of the kind was made 

 by Viviani. 



From the explanatory figures of this machine, which are in the 

 41 Libro de Saggi," published by the Academy, and which you see 

 before you, you will be able to understand how. it was in reality a true 

 mercurial machine, with which the academicians made a great number 

 of experiments, to which I shall allude further on. 



A no less powerful intellect was that of Borelli, a Neapolitan. A 

 mathematician, a physician, an astronomer, he occupied himself with 

 all subjects, and thus supplied himself with ample materials for future 

 discoveries. He studied the reciprocal attraction of floating bodies 

 (galleggianti\ and discovered its theory ; he was the first to observe the 

 variations of the barometer with the changes in the atmosphere ; he 

 considered the question of the freezing of water ; he planned the ex- 

 periments which were decisive against the idea of the positive light- 



