Kurs VOLUCELLA. 203 



energy of their movements at hrst, the)' usually increase in vigor 

 and speed until after midnight and scarcely grow less before morn- 

 ing. Nothing affords them so much gratification as a large wheel 

 which is placed inside, the cage. Into this wheel they jump when- 

 ever aught disturbs or pleases them, and even when quite hungry 

 they often find it necessary to take a few turns before commencing 

 their meal, after which exercise they draw themselves into a bunch 

 with the tail over the back, after the manner of squirrels, and set 

 briskly to work on the nut or other food they may have 

 received. They are almost as fond of riding as of running, and 

 work their passage by running till the wheel is in rapid motion and 

 then clinging to its wires, and so are carried around and around, 

 the pure white of the under side of the body contrasting prettily 

 with the soft brownish-gray of the back and sides as each comes 

 into view. When both are in the wheel one often rides while the 

 other turns the wheel, the latter bounding over the other as each 

 turn brings him around, and, no matter how rapidly the wheel 

 turns, these movements are executed with perfect exactness and 

 gracefulness. Being desirous of knowing with some degree of 

 accuracy how rapidly the wheel moved, I made some experiments 

 for that purpose and found that the usual rate of revolution was 

 from sixty to over a hundred and twenty times a minute, and, as 

 the wheel is forty-four inches in circumference, when its rate is the 

 latter of the two numbers named, the squirrel turning it must 

 travel four hundred and forty feet a minute, or about five miles an 

 hour, a distance requiring a great many steps when they are 

 so short as squirrels must take. The sides of the wheels are formed 

 of spokes radiating as in any wheel, these spokes are only five 

 inches apart at the circumference and of course constantly grow 

 less toward the centre ; yet through this narrow space which passes, 

 when the wheel is at full speed, in the sixteenth of a second, they 

 dart in and out with perfect ease. So quickly do the)- move that 

 the eye can scarcely follow them; one instant a squirrel is in the 

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