THE YOUNG NATURALIST. 



TESTING THE CLEANNESS 

 OF THE AIR.— Professor De- 

 war has recently devised a new 

 method of testing the contami- 

 nation of the air, A short time ago he 

 exhibited before the Royal institution 

 two samples of liquid air in glass tubes 

 — one was made from air which had 

 been washed to purify it from dust, 

 soot, carbonic acid and other impuri- 

 ties. This, when condensed, was a 

 pale blue liquid. The other sample 

 was made by condensing the air of the 

 lecture-room in which the audience was 

 assembled, and was an opaque, black- 

 ish fluid, resembling soup in appear- 

 ance. 



THEIR WONDERFUL EYES.— 

 When a fly comes from an egg, one of a 

 family of thousands, it is soft, pulpy, 

 white, eyeless, legless. When mature it 

 affords the student one of the most mar- 

 velous fields in all nature, with its nerve 

 clusters and brain, its feet like the 

 hoofs of a rhinoceros, a thousand hol- 

 low hairs on each footpad, the wings, 

 which make 15,000 vibrations a second, 

 and the eyes. There are 8,000 of 

 these, each a perfect lens. 



A fly's eyes are hard, immovable and 

 retain their form after death. As a fly 

 cannot turn its head it has eyes in all 

 directions. So small are these eyes 

 that 1,000,000 would not cover the sur- 

 face of a square inch. Each eye meas- 

 ures a thousandth part of an inch and 

 the color is amost always red. 



Each of these eyes is a lens and pho- 

 tographs have been taken through 

 them. The lenses are of varying kinds 

 — some suitable for looking off at a 

 distance, others for things close at 

 hand. Occasionally with his thousand 

 eyes a fly is deceived. This is evi- 

 denced when a blue-bottle inside a 

 room heads for the open country. He 

 does not see the window glass and the 

 thump with which he strikes and the 

 angry buzz which shows his discom- 

 fiture show how mistaken he was. 



To prove there is nothing extraor- 

 dinary in a fly's having 8,000 eyes it is 

 known that a certain beetle owns 50,016 



eyes; a certain butterfly 34,710, a com- 

 mon dragonfly 25,088, and a silkworm 

 moth 12,500. 



NOTES ON ANIMALS.— The in- 

 sect effects its breathing, not as men 

 and animals do, by the lungs, but 

 through openings in all sides of the 

 body. It has an intricate system of 

 tubes running through all parts of its 

 person, through which the air is brought 

 in contact with the legs, wings, and so 

 on. These tubes are each protected 

 by delicate membranes. In the fly 

 there exist certain air pouches in addi- 

 tion to the tubes, which serve as reser- 

 voirs of air. 



It is generally supposed that instinct 

 unerringly teaches birds and insects the 

 best way in which to build their homes 

 or nests, and also to provide for their 

 offspring. The following incident, re- 

 cently under personal observation, will 

 show that instinct is not always infalli- 

 ble, says the Scie7itific Americati: "A 

 friend placed three small empty vials 

 in an open box on a shelf, in an upright 

 position in close contact, and they 

 were uncorked. A short time after- 

 ward it was a matter of surprise to find 

 that these had been appropriated by a 

 female mud wasp. She had placed a 

 goodly number of spiders in the center 

 vial, doubtless intended to serve as 

 food for her future brood; then pro- 

 ceeded to deposit her eggs in those on 

 either side. She next closed tightly 

 the mouths of all three receptacles with 

 a hard lime cement. Having finished 

 her work, she then doubtless went on 

 her way, satisfied all had been done for 

 her offspring that a thoughtful mother 

 could do. But just think of the sensa- 

 tions of those little wasps when they 

 come into existence, for, while starving 

 in their sealed cages, they can plainly 

 see, through the impenetrable glass 

 walls, the bountiful supply of food 

 which was provided for their use. 



It has been supposed that the swal- 

 low is more rapid in its flight than 

 almost any winged creature, but the 

 dragonfly easily outwings it. An ob- 



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