44 Questions Jbr Solution relating to Meteorology, 



nothing will counteract its expansive tendency when it is brought 

 to the surface, where the pressure of the water from without is 

 removed ; it will then either escape or burst the apparatus. 

 To guard against this, a free issue must be provided for all 

 possible expansion either of the water or air. For this purpose 

 the fixed bottom is furnished with a lateral canal which leads to 

 a gas-bladder ; the latter having been first filled with water, then 

 emptied and pressed together before the apparatus was sunk. 

 This bladder will receive all the air which the water may dis- 

 engage on approaching the surface ; and, if any be disengaged, 

 it will return more or less inflated. Then, by closing the stop- 

 cocks with which the canal is provided, it may be separated 

 from the vessel containing the water, its volume measured, and 

 the enclosed air analyzed ; after which what may still remain in 

 the water may be examined, and likewise any other substance 

 which the water may hold in solution. Such is the apparatus 

 which has been entrusted to the commander of the Bonite ; and 

 the zeal as well as intelligence of that officer, affords us the as- 

 surance, that it will be usefully employed, under his directions, 

 to solve the various questions relating to terrestrial physics indi- 

 cated above ; questions which, besides their purely scientific in- 

 terest, have an additional importance attached to them, by the 

 knowledge which their solution would supply respecting the 

 permanence or changeableness of our atmosphere, and the con- 

 ditions of the existence of living creatures found in the depths 

 of the sea. 



Marine Currents. 

 The Atlantic Ocean, South Sea, and the Mediterranean, are tra- 

 versed by numerous currents, which are the more dangerous from 

 carrying vessels out of their proper course, without the pilot 

 suspecting their influence, and, in cloudy weather, he has no 

 means of ascertaining it. Among phenomena relating to the 

 sea, and considered in the double relation of theory and prac- 

 tice, there is certainly none more deserving of the highest degree 

 of attention on the part of navigators of every country. The 

 numerous memoirs and works specially appropriated to the sub- 

 ject, such as those of Ducoudray, Romme, and even the posthu- 

 mous and able treatise of Major Rennel, which has just appear- 



