90 Mr. J. Y. Buchanan. On a licmarkaUe Effect [May 14, 



distributed much more uniformly over it than is the case in the brass 

 tube. In the latter the effect is very powerful and very local. In both 

 cases the effects which we see have been produced in a moment of time, 

 and are properly speaking, the effects of violent shock. It is remarkable 

 that in the ball the equatorial zone which has the welt to stiffen it should 

 be the field of all the disfigurement, while the polar areas which have 

 no strengthing have not been exposed, or at least have not yielded to 



strain. 



If we examine the brass tube, figs. 1, 2, we see that, with the excep- 

 tion of the portion nearly in the middle which held the sealed glass 

 tube, the case has perfectly preserved its cylindrical form. The dis- 

 tortion or crumpling affects only the part where the tube collapsed, 

 and it is evident that it did not occupy a truly axial position, but 

 lay nearer that part of the brass envelope where the ears for 

 attachment to the sounding line are situated. Here a most formidable 

 corrugation (fig. 1) has been produced, the metal being pinched into 

 a fold so as almost to meet inside. Besides this, there are two minor 

 corrugations. A greater thickness of water intervened between this 

 part of the brass envelope and the enclosed glass tube, and the small effect 

 produced shows that the difference of pressure within and without the 

 brass tube was here comparatively small. It will be observed that the 

 butt-joint of the tube has been opened at fig. 2; but this is a 

 secondary effect due to the distortion. 



The brass tube, as it stands, is a manometer or pressure gauge which 

 records the distribution of pressure in it while filled with and immersed 

 in water, during the instant of time when, while the pressure on all 

 sides is very great, the pressure at a locality in the interior suddenly 

 becomes nothing or very small. The effect of this sudden difference of 

 pressure has been concentrated on the part of the brass tube nearest to 

 which the glass tube was situated. Here the diminution of internal 

 volume of the brass tube produced by the principal corrugation must, 

 from rough measurements, be very nearly equal to that of the glass 

 tube which collapsed. At first sight it appears remarkable that on 

 the collapse of the glass tube, when it was free to the compressed sea 

 water to fill up the void with water through the two open ends, 

 instead of doing so, it filled it by pinching up the stout brass of which 

 the tube was made, to such an extent as to obliterate the void. 



The experiment shows us that it was easier in the time to pinch the 

 envelope of brass than to shove in the plugs of water at both ends. 

 The complete absence of distortion or disfigurement of the upper and 

 lower portions of the brass tube shows that the tension of the water in 

 these two portions of the tube was not materially diminished in the 

 time between the collapse of the glass tube and the occupation of its 

 place by the corrugation of the envelope. In considering this experi- 

 ment, we must distinguish between the tension and the pressure of the 



