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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 



