196 Intelligence and Miscellanies. 



The instances related of bottles containing fresh water 

 having their contents replaced by salt water, are owing to 

 the same principle as the replacing of the air of the bottles 

 by sea water ; for fresh water being of less density than salt 

 water, it would pass out, to make way for a denser fluid, or 

 the same kind of fluid, made denser by saline substances. 

 It is my intention to repeat this experiment during the next 

 calm, should one occur. 



The most, simple mode of trying the experiment which I 

 made, would have been with a bottle whose mouth was 

 hermetically sealed. The want of time before I left New 

 York, prevented me from having one prepared. 



Note. — Professor Vanuxem, when these experiments were 

 made, was on his way to the city of Mexico, where he will 

 reside for two years. He may be addressed through Behr- 

 man & Muller, La Vera Cruz. — Ed. 



10. Effects of friction on board of Ships of War. 



Extract of a letter from Lt. James Glynn, of the U. S. Navy, in answer te 

 certain enquiries by the Editor. 



New Haven, Conn. Nov. 16, 1827. 



Sir — On board of our national ships of war, where des- 

 patch in performing any evolution is a consideration second 

 to safety only, it not unfrequently occurs that the pullies are 

 destroyed by the friction of the sheave, or wheel on the pin, 

 or axle, about which it revolves ; or against the shell or case 

 that contains it. In one instance I have known fire produc- 

 ed in this way to break out into a full distinct blaze. On this 

 occasion, 1 think iron was in contact with iron, the tempera- 

 ture of the air was agreeable, and the pully or tackle had 

 been in active operation for perhaps half an hour, when a 

 heavy boat was attached to it for the purpose of being hoist- 

 ed on board, and a velocity of revolution given to a wheel 

 of four or five inches diameter, equal to what might be com- 

 municated by the seamens running fore and aft the deck, 

 with the chord of the pully in their hands. The effect was 

 so unexpected, as to put at an imminent risk, both property 

 and lives. 



Similar, and nearly allied to this is the fact, that on board 

 of large vessels, anchoring in high winds, the friction of the 

 cable round the bitts, (windlass of the merchant vessels,) is 



