138 SECTION PHYSICS. 



propagation of heat ; on the propagation of sound in vacuo, v.-hcn it 

 was wisely remarked that the sound generated could be communicated 

 to the exterior air, by the very partitions of the recipient in which the 

 sonorous body was closed ; on the attraction of the loadstone ; en. 

 capillary phenomena, independent of atmospherical pressure ; on the 

 boiling o water in vacuo ; on the bursting of air-bubbles by cold ; 

 and, finally, on the various ways in which many animals are afTected 

 when placed in vacuo, or in very rarefied air, such as leeches, snails, 

 grasshoppers, butterflies, lizards, flies, little birds, crabs, frogs, and 

 different kinds of fish, and they paid particular attention to the effects 

 produced on the swim-bladders of the latter. With regard to these last- 

 mentioned experiments, and especially to those which refer to little 

 birds that die immediately, and even when succoured in time do 

 not fly away, it is well known that in one of Boyle's experiments a 

 lark lived ten minutes in vacuo, and a goose seven minutes. But, it 

 is added, that whoever reflects upon the different ways of producing 

 the void in these two cases will perceive that the experiments, far from 

 proving contradictory to one another, agree most admirably; inas- 

 much as where in the one case (Boyle's) the air is thinned by succeed- 

 ing attractions with very slow and little less than insensible acquisi- 

 tions ; in the other, by the extremely rapid descent of the quicksilver, it 

 is immediately reduced to that last degree of rarity and thinness, which 

 cannot be of any avail for respiration. And from this we can gather 

 that even at that time the superiority of the mercurial pneumatic 

 machine over all others was perfectly well known. 



As an introduction to the experiments on the compression of water, 

 Magalotti writes " Although the truth is not always arrived at by the 

 first experiment, that is not the case because the first idea cf the ex- 

 periment is not very often quite adequate to obtain the truth ; but it 

 may sometimes happen because the materials and means which are 

 used to carry it out practically are not adapted to that purpose ; and 

 although these experiments cannot contaminate the purity of the 

 theoretical speculations, they are nevertheless unfitted to second them, 

 on account of the materials employed. But not for this reason must 

 these experimental inquiries into natural phenomena be deemed to 

 have failed ; because, although at times we do not succeed, by means 

 of them, in coming to the bottom of the truth, which was first of all 



