Notices respecting New Books. 145 



of the wave passing again through succeeding portions of the 

 atmosphere of different density, may be so wasted and frittered 

 down as to be incapable of affecting the tympanum. 



My observation respecting the intensity of sound is not con- 

 fined to the Peak. At the town of Orotava, situated about two 

 miles from the sea, the noise of the waves in the morning 

 occasionally had a grave low tone: at the same time the air 

 appeared to be particularly dry, and distant objects were very 

 indistinct. Towards the middle of the day, or the beginning 

 of the afternoon, the island of Pal ma, nearly sixty miles 

 distant, could be distinctly seen ; and the ridge of mountains 

 that surround the valley of Orotava were apparently brought 

 so close, that the vegetation upon them could be observed: 

 at the same time the sound of the sea invariably passed from a 

 grave to an acute sound. The natives prognosticate rain when 

 this particular clearness of the atmosphere takes place ; and I 

 have generally found them correct. 



But to return from my digression. At various times in the 

 night I observed meteors, like rockets, with luminous points, 

 shooting about in the atmosphere, apparently at an elevation 

 not much greater than the top of the Peak. Their appearance 

 was different from those ignited vapours commonly called 

 falling- stars, and their course was different, as they generally 

 moved in a horizontal direction. 



At no period of the night did the thermometer fall below 

 34°, and the average height of it from 5 P.M. to 5 A.M. was 

 37°; but from the great rarefaction of the air, it appeared by 

 the feelings to be considerably below the freezing point. 

 [To be continued.] 



XXII. Notices respecting New Books. 



A Treatise on Hydrostatics and Hydrodynamics for the Use of 

 Students in the University. By H. Moseley, B.A. of St. John's 

 College. Cambridge, 1830. 



THIS work contains a proposition deserving of notice, as being 

 in a great measure new, and of considerable importance in the 

 theory of the motion of fluids. The proposition may be thus ge- 

 nerally stated : — If fluid of any kind be moving in such a manner 

 that at the same point in space the velocity is constantly the same 

 in quantity and direction, and if x, y, z, be the forces impressed at 

 any point whose coordinates are x, y, z, and v be the velocity at 

 this point, then will 



f. d JL =f { Xdx + Ydy + Z dz) - -£- + c 



Euler has given in the Berlin Memoirs, 1755, a proof of this 



theorem for incompressible fluids, seemingly without being aware 



N.S. Vol. 8. No. 44. Aue. 1830. U that 



