Page:Popular Science Monthly Volume 91.djvu/541

 Popular Science Monthly

��This Bird's Nest Is Evidently a Two -Room Apartment

BIRDS, like persons, sometimes do strange things. Here is a double nest of a "Chipping" sparrow, an un- usual type indeed for this bird. A guess at the ex planation would be that a roving bird, probably a cuckoo, which is notoriously lazy and homeless, deposited an egg in the sparrow's nest while she was taking a bit of recrea- tion. When the spar- rows discovered it they busied themselves making an addition to the original nest, to which they transferred their own eggs, leaving the intruder's in the old nest to addle.

���A freak nest built by a pair of sparrows probably because of a strange egg laid by another bird in the original nest

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curious vehicle which plunges through the waves as easily as any boat and which runs on land as easily as any automobile; for Delia is both boat and car.

Now comes M. J. Ravaillier, a French inventor, with a smaller vessel of similar design. The accom- panying photographs show this boat on land and emerging from the Seine. It measures about sixteen and one- half feet in length and seats four persons. Its steel hull is sup- ported in front and rear by the usual axle and wheels. The axles fit into watertight tubes which pass through the hull. The craft is propelled by a twelve-horsepower engine. Two distinct transmissions are used.

��Which Is It— Boat or Motor Car? It Travels on Both Land and Water

"T~\ELIA the motor duck" is no doubt J_y remembered by readers of the Popu- lar Science Monthly. For the benefit of those who did not see her in our issue of March, 1916, let it be said that Delia is a

���The boat is hauled up out of the water with ropes. After which it proceeds over the land route with a chauf- feur at the driving wheel

��It Takes About 150 Pounds Pressure to Break an Egg

NATURE executed a wonderful piece of workmanship when she put the shell around the egg. Most of us have an idea that the shell is fragile. It is — sometimes; but scientists have established the fact that the average pressure under which white eggs break is one hundred and twelve pounds. Strange to say, brown eggs are stronger than white ones. It takes a pressure averaging one hun- dred and fifty-five pounds to break them, the minimum being one hundred and twenty-five pounds and the maximum one hundred and seventy-five pounds. When it is considered that the thick- ness of an aver- age eggshell is .013 and the di- ameter of the eggs one and three-quarter inches, some idea may be formed of their enormous resistance.

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