NATURAL PHILOSOPHY. 155 



of experiments made by him, their object being to ascertain the fric- 

 tion of the water on a vessel, or other floating body, rolling in it. 

 In making his experiments, he used a cylindrical model, thirty inches 

 long, and twenty-six inches in diameter, whose weight was two hun- 

 dred and fifty-five pounds, avoirdupois. The cylinder was in the first 

 place put into a cistern without water, and made to vibrate on knife 

 edges passing through its axis. A pencil, projecting from the model, 

 in the direction of the axis of the cylinder, on the surface of another 

 movable cylinder, marked out, upon paper placed on this last cylinder, 

 the amplitude, or extent, of each oscillation. The cylinder was deflected 

 over to various angles, by means of a weight, attached by a string to 

 the arm of a lever fixed to the cylindrical model. The table given by 

 Mr. R. shows that in these cases the model vibrated to an angle, in 

 general 6' less than the angle to which it was deflected. When the 

 cylinder oscillated in exactly the same circumstances, except that it was 

 surrounded by salt water, it appears that the angle of vibration was 

 about 30' less than that of deflection. This shows clearly, that when 

 vibrating in water there is a falling off in the angle of about 24' from 

 the vibration out of water. This decrease must be attributed to the 

 friction of the water on the surface of the cylinder. The author 

 thinks, from calculations, that the amount of force acting on the sur- 

 face of the cylinder necessary to cause this decrease is not equally dis- 

 tributed over it, but that the amount on any particular part varies as 

 the depth. Some experiments confirm this view. These, with other 

 experiments, made under the direction of the Admiralty, go to show 

 that when " a sudden gust of wind is applied to the sails of a vessel, 

 or any cause which acts constantly during one oscillation, the ulti- 

 mate amplitude of deflection will be double the amplitude which the 

 gust of wind will permanently deflect the vessel." London Athenaum, 

 Sept. 



LIEUT. MAURY ON WINDS AND CURRENTS. 



LIEUT. MAURY is still pursuing his favorite theory of winds and 

 currents, which has already been productive of much good to the 

 commercial world, although the observations as yet made have been 

 very limited compared with those which must be made before a cor- 

 rect knowledge can be obtained of the winds and currents of the dif- 

 ferent oceans. His "Wind and Current Charts" are so made, that" 

 at a single glance the navigator is able to see in what portion of the 

 Atlantic Ocean he shall probably find the most favorable winds and 

 currents. He has adopted the plan of dividing the ocean into sections 

 of five degrees each, and the track of each vessel is laid down across it 

 in colors according to the seasons of the year, and in characters accord- 

 ing to the month, while the symbols for the winds are so contrived that 

 they show at once both its direction and strength. In this way the 

 charts show at a glance the prevailing winds, the temperature of the 

 water, the set and velocity of the currents, the variation of the compass, 

 &e. The results gained by these charts are numerous; we give the 

 most important of them. 



