4i B Erroneous Nations concerning a Vacuum. [Book V. 



that water would mount only to a certain height, after 

 which in appeared to them, by the void fpace which 

 they found, that nature was reconciled to a vacuum, 

 or at leaft fuffered this defect without thofe terrible 

 effects which ancient writers had predicted from it. 

 This -apparent caprice, on the part of nature, was com- 

 municated by the engineers to Galileo, who paid fome 

 attention to itj though, previous to this accident, he, 

 as well as all others, had fatisfied himfelf with the com- 

 mon opinion of the horror which nature was fuppofed 

 to entertain for a vacuum. He was at length con- 

 vinced, by reiterated experiments, that water would 

 rife only to about thirty- two feet perpendicular in 

 pumps, and that the remainder of the pipe or tube, if 

 it was longer, would be empty. He could then no 

 longer retain the opinion refpecting the horror of a 

 vacuum, but began to conceive that this horror had 

 its limits, and that thefe phenomena might proceed 

 from a phyfical caufe very different from that to which 

 they had hitherto been attributed. What he had fuf- 

 pected, Torricelli, his difciple, proved by direct ex- 

 periment. He firft made it appear in the year 1645, 

 that a column of air, as it exilts in the atmofphere, 

 may be placed in equipoife with a column of another 

 fluid, which has the fame bafe ; at length, to avoid the 

 inconvenience of a long pipe, inftead of water he made 

 ufe of mercury. He took a glafs tube (Fig. 5.) of 

 about three feet in length and two or three lines diame- 

 ter, hermetically fealed * at one end, and open at the 

 other; he filled it with pure mercury, and having 

 (topped the orifice with his finger, he reverted the tube, 

 and placed the open end in a veflel full of rhe fame 

 tfiercury. He had no fooner removed his finger, than 

 the column of mercury, which was about thirty-fix 

 * Clofed by melting the glals, and confolidating it. 



inches 



