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the motion of a body in a resisting medium. This effect of 
the air’s resistance can be shown to be unusually great in the 
case of a body (like the boomerang) composed of two straight 
arms united at a large angle, and projected with a revolving 
motion ; and hence the large resulting deviation in this case, 
amounting (as is known) to 180°. Mr. Lloyd observed, 
however, that this anomalous deviation was by no means 
peculiar to a projectile of this form; and that there were 
even other shapes which exhibited the property in a more 
remarkable manner. 
The other peculiarity in the flight of the boomerang, 
namely, its alternating ascents and descents, were ascribed 
by Mr. Lloyd to a nutation in the axis of revolution ; the in- 
strument (on account of its flat shape) being compelled to 
move in its own plane, which is also the plane of rotation. 
The motions of translation and of rotation of a heavy body 
in a resisting medium are not independent of one another, as 
they are in vacuo ; and hence the variations of the progres- 
sive movement will produce corresponding variations both 
in the velocity and direction of the rotation. 
— 
Professor Lloyd read a letter from Mr. Knox, detailing 
some results of the performance of his rain-guage, during 
the months of August, September, and October, and de- 
scribing a mode in which these results were graphically 
registered. The following is an extract : 
“Drawing from a centre eight lines, to correspond with 
the cardinal and intermediate points, I take on each line 
a space respectively proportional to the amount of rain that 
has fallen from that point during any month; connecting the 
point so taken, I get a curve (or rather an eight-sided 
figure) which exhibits at one view both the amount and 
character of the rain during the month. It also enables the 
observer to compare one month with another, and likewise 
to get a mean curve for the season, which may be of great 
use in determining local climate. It is probable that the 
