the rushing waters. The cut in the bank is 139 feet above sea level, Calexico is at ocean level and the sink 287 feet lower. The advance floods poured into the depression through an ancient river mouth with terrific speed. A mighty work appeared, cutting backward. The water backed up stream at times, with a rate of half a mile in each twenty-four hours. The roar was fearful. The falls receded, passed to the west of Imperial, Brawley and El Centro, and then drew near to Calexico. Levees were erected, Calexico was The river on July 2 was backing

saved, but Mexicali vanished.

up towards the Colorado cut and was two miles above Mexicali.

WASTE GATE AT SHARP'S HEADING.

This is east of Mexicali, Mexico, and regulates the system of canals belonging to the California Development Company. From a photo by Rissinger, Calexico.

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The Salton Sea is now 45 miles long and from 10 to 18 wide. On July 1, I went with a party of civil, hydraulic and railway engineers on the steamer Searchlight from Yuma down the river to the cut. The bed of the mighty Colorado below the cut was dry! No water flowed to the gulf, all went to the Salton Sink. The cut was 4000 feet wide. Trees were falling into the rapid current. I saw the vast plans as drawn up by the engineers. A great dam is to be thrown across the break. These plans are technical and can be explained only in an engineering magazine. The great scheme is in charge of Engineer H. T. Cory, Chief of the California Development Company. It is hoped that the arduous

work will be finished before January, 1907, and the floods controlled. If not, then the entire Salton Sink will be filled to the level of the primeval ocean, even to the ancient beach line. The Colorado in that event would never enter the gulf again, for its new bed is now lower than the old. Climatic changes would no doubt occur with the formation of a permanent new sea. If the dam is a success, then the fierce rays of the sun will again evaporate the water and the sea will vanish, leaving a deep layer of silt all over the layer of salt.

WONDERFUL ILLUMINATION OF THE ANCIENT SINK.

On my first visit, I secured an ordinary view of the Sink and its low down central sea. But on the second journey, it was my good fortune to behold a scene of splendor. The sun was just far enough north to escape a distant peak in the west and pour floods of slanting rays into the entire depression. I saw it all, for five minutes; every outline of the ancient ocean beach and the new sea. The region is simply wonderful. On July 1, I ascended a high place in Yuma and looked at the Sink with a glass from the east. I saw the giant rim of this cup in the earth. The geology of the entire region was revealed in all its scenic splendor.

LOWE OBSERVATORY, August, 1906.

1

THE DOG'S RACING LEVERS AND BURROWING

OUTFIT.

ALTH

BY WOODS HUTCHINSON, M. D.

LTHOUGH a dog's teeth are the most important thing in his make-up, his legs and feet are only a shade less so. And their purpose is equally clear, even if we had never seen him use them. They are to run with and to stand upon, and hence naturally placed "one at each corner," as the school-boy explained in his immortal essay.

But why are the back pair so different from the front ones? As the dog stands at ease, you can see that his front legs are almost perfectly straight and upright, like props supporting his chest, and the only joint you can make out in them is the "elbow" close up to the body. The hind legs on the contrary slope first slightly forward from the hip to a joint called the "stifle," then a long slope backward to another joint the "hock" and a short slope forward again to the paw. They are anything but straight, indeed "crooked as a dog's hind-leg" has passed into a proverb and you can see two very distinct joints. And as a dog's back is as high at the hips as at the shoulder, and a straight line is the shortest distance between two points (in this case his body and the floor) it necessarily follows, as I think your eye will tell you, though you can measure it if you choose, that the hind legs are distinctly longer than the front

ones.

If you will look carefully at this skeleton (Fig 1) you will see that the bones are not only longer but thicker. Now which pair would you say had the heavier part of the work to do in running? You will generally find in animals, that of two similar structures or organs in the same animal, or even in two animals of the same family, the smaller has the less to do, or is of less importance.

Go and watch the dog as he runs and see if this "trial-conclu

sion" is right. A gallop is the best gait to study first, because this is the only pace in which both hind-legs are moved together. If you can get him to run past you slowly enough, you will see that he is moving in a series of bounds or short leaps, throwing himself forward with his hind-legs and catching, or propping, himself with his front ones.

Get him to jump a fence or over a log, and you will see still more clearly that he brings his long, crooked, hind legs well forward under him for the spring, launches himself into the air by suddenly straightening them and catches himself on the other side upon his fore legs until he can bring his hind legs in under him again.

Now go watch his gallop again and you will be able to make out what part each pair of legs takes. He springs forward from his hind legs, catches himself with the front pair just long enough to "recover" or swing the hind one well under him again for the next spring; another "prop" with the fore legs, while the hind are coming forward into position again; another spring-and that is the gallop. A rapid succession of quick flat-jumps running into one

another.

Mind it is only a very slow gallop that you will be able to take to pieces in this way, for if the dog is going at all fast, his jumps melt into one another and his legs make a confused blur,

like the spokes of a wheel. And to make it worse, when his hind feet come forward for the next spring, they do not only swing up to the planted fore feet, but right past them on either side and land

Showing plunging-forward character of gallop in both horse and kangaroos. The horse must prop himself with his fore-feet each leap; the kangaroo bounds so high into the air that he has time to swing his hind legs in under him before he alights without using his fore feet at all.

Fig. 2.

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well in front of them, so that at one point in his stride the dog is doubled up like a double-bladed clasp-knife with the blades half open or like a boy when he vaults over a post or "takes a back" at