in Fluids. 393 



the distance of i Inch from each other. In the middle 

 of the top of this brass frame there is a circular open- 

 ing about \ an inch in diameter, into which a project- 

 ing cyhndrical brass tube, about half an inch in length, 

 is soldered ; and in the middle of the bottom of the 

 frame there is a similar tube which projects downward. 

 The first of these openings serves for introducing into 

 the flat box the liquid with which it is filled, and the 

 other for drawing it off; and they are both well closed 

 with fit stopples of cork. 



On both sides of this brass frame there are deep 

 grooves into which the panes of glass are fitted, and the 

 box was made water-tight by luting the joinings of the 

 glass with the frame with glazier's putty. On the out- 

 side of the frame there are thin projections of sheet 

 brass, by means of which the box was fixed in one of 

 the sashes of a window in my room, where it occupied 

 the place of a pane of glass, which was removed to make 

 way for it. This window fronts the southeast, and con- 

 sequently is exposed to the sun a great part of the day. 



Having provided a sufficient quantity of the saline 

 solution (of the same kind as was used in constructing 

 the instrument above mentioned, contrived for render- 

 ing visible the internal motions in Fluids), and having 

 mixed with it a due proportion of pulverized yellow 

 amber, I now filled the box half full with this mixture, 

 and as the air in the room was considerably warmer than 

 that without, I expected that the motions in the liquid 

 occasioned by the passage of the Heat would immedi- 

 ately commence. 



This actually happened ; but how great was my sur- 

 prise when, instead of the vertical currents I expected, 

 I discovered horizontal currents running in opposite di- 



