68 Screntifie Intelligence. 
Near the upper end of the outer tube, there are three spiral 
Soeligs: fixed at the top and united at the bottom by a plate or 
disk, from which the central copper tube is suspended. Froma 
stem fixed to the center tube or float, and moving with it, a string 
or chain leads over a single pulle ind ewes horizontal motion to 
the pencil carriage of the recording apparatus. 
The distance that the central tube is to move, vertically, is ad- 
justed to agree with the required range of the pencil upon the 
record Rogen ab placing within it suitable weights. 
As the glycerine falls or rises in the annular space between the 
iron tube and the central float, the spiral spring at the top is more 
or less extended, the extension being uniform on account of the 
cylindrical form ‘of thre floa 
It is not necessary that the India-rubber bag be enclosed in a 
perforated box for the purpose of preventing oscillation: as it is 
always submerged, and the pressure upon it is equal to the weight 
of a column of water, having —- ~ at the bag, and its summit 
at the mean level of the surface 
This instrument has been opabeeadted by the United States 
Coast Survey, and is now in operation at the tidal station in the 
Boston vat ard, 
4, American Weather Notes ; by Puy Harte Cuase. (Read 
before the pete rican Philosophical Society, March 3, 1871.—The 
signal service observations of o Tar Department have already 
shown the value both of Buys Ballot’s law and of Capt. Toynbee’s 
Somes in predicting changes of wind, page if due regard 
| pa e barometric variations of the t o previous days. 
thers seem to be explicable by natural c 8 of position 
and - sical configuration, which must be seerative at all seasons. 
inds varying like the land and sea arena, are often trac 
differences of tem mperature in the n neighborhood of the great lakes, 
and of mountain peaks and ridges, 
(2.) The wind, especially in the Southern States, often blows di- 
rectly in the line of the greatest barometric gradient. But even 
- in such cases, after a few hours continuance, it tends toward the 
acinnuth i indicated by Buys Ballot’s law. 
(3.) The isobaric lines are, jaacte ie —— of less relative impor- 
hye Currents with an coset Breer wang’ controlled by areas 
of high barometer, are notably common. Keversals of wind, as 
from N.E. to S.W., are, therefore, frequent after the passage of 
