warehouse on the night of the sixteenth of April.

The police took immediate charge of the case. There had been a little rain on the evening before and they found two lines of footprints where a man had come to the warehouse door and returned from it. They were able to follow these tracks to the shop of an Austrian who dealt in antiques. In America this man would have been called a junk dealer, since he possessed only a single room with a dirt floor, situated in the environs of the city and filled with articles of but slight value.

The police were able to show that the Austrian had made these footprints. But here the mystery presented itself: When the man understood what the police were after he at once said that he had gone to the warehouse, on the evening in question, in order to inquire whether the merchant had for sale any of the articles in which he commonly dealt; but that when he arrived the warehouse was closed and he had returned to his shop.

The police searched the shop with German thoroughness, but found no trace of the bale of rugs. They were able to see that the man had not left his shop after he returned from the warehouse, for there were no other footprints in the wet earth in the environs of the shop; evidently he had not gone out after he returned. And, also, it was evident that no bale of rugs was anywhere about his shop.

The police, profoundly puzzled, returned to the merchant.

They thought he was not precisely clear about the bale of rugs he said was stolen. He was not able to produce an invoice of it. But he said it had been a long time in the shops, was of great value, and showed them the outline in the dust on the floor where it had been lying.

Unable to unravel the mystery, the police sent to the authorities for an expert. The expert came and looked at the two lines of tracks. He at once said that the man who came to the warehouse on the night of the sixteenth of April had come empty handed, but had unquestionably gone away carrying something heavy. He explained that when one is walking without a burden one travels in a straight line, turning the feet out at an angle common to that individual. (See Frontispiece, Figure 16.) But that when one is carrying a heavy burden one invariably walks with the feet straight and the legs wider apart, in order to give the body a more stable support under the added weight. (See Frontispiece, Figure 17.)

Thus, when we find a line of tracks going straight ahead close together with the feet turned out, and afterward these same tracks wider apart and the feet set straight, we may be certain that the person who had begun to walk without carrying anything had now taken up a burden to carry.

It may be interesting to add the method by which the expert discovered the concealed rugs. When he arrived at the Austrian's shop he took a kettle of water and poured it on the dirt floor. He went over the

whole floor very carefully. Presently at a certain point he directed the police to dig up the floor. They found the bale of rugs buried at this point.

The Austrian had dug up the floor, concealed the rugs, and tramped the earth down so that the eye could not detect anything unusual. But the expert knew that if the earth of a hard dirt floor had been recently disturbed, and one poured water on the surface, air bubbles would appear. Thus, when he found these air bubbles he was certain the earth of the floor had been disturbed.

Even a cursory examination of the German diagrams will give anybody a good deal of information about how a man walks. In Figure 18 (Frontispiece) the line A A running through the border of the heel is called "the line of march." The lines CC show the direction of the footprint with respect to the line of march. The Germanic authorities maintain that when the normal person walks in a straight line a line drawn through the center of the heels will also be a straight line that is to say, the heels go ahead precisely on a straight line.

But other investigators are inclined to doubt this. They say that when the normal person walks in a straight line this line of march will touch only the inner border of the heel instead of running through the center of the heel. It may be that with the German military step the line would go through the center of the heel. But in nonmilitary countries, like America, it will usually be found, in normal in

stances, that the line of march touches the inner border of the heel and not the center.

This is true of normal persons walking in a straight line. But in abnormal persons-sailors, fat men, the aged and infirm, and children-the line running through the heels will be zigzag, like the line B B in Figure 19 (Frontispiece).

The Germans say that persons of leisure turn the foot out more in walking than do workmen or persons in trades. It is thought that women turn the foot out less than men. It is also believed that certain races, like the negro, walk with a very exaggerated foot angle; while the North American Indian travels with the foot almost parallel to the line of march.

Gross undertook to demonstrate the mechanical factors in the act of walking. These factors are outlined in Figure 20 (Frontispiece). He points out that when one takes a stride the perpendicular distance from the hip joint to the ground is reduced, and that as the stride is increased this distance is lessened. Thus, with each step, as the body is lowered, it has to be again lifted. This, he said, was the reason why is was easier for a man to run than to walk rapidly with a long stride. See Figure 21 (Frontispiece).

It is said that one day, when Gross was driving through the park with an acquaintance, his friend pointed out that several persons had gone along in the dust on the road before them. He asked Gross whether he could tell him who the persons were.

The professor got down out of the carriage and drew a mark across the road with his cane; then he stepped off fifty feet along the road in the direction in which the tracks were made and drew another mark across it. He then counted the number of footprints in each of the three tracks within that distance.

One of the lines of tracks showed fewer prints than the other two. Gross, therefore, said that this track had been made by a tall man. The tracks showing the greatest number of prints indicated a short person, while the third track was that of an old woman with a stick.

The persons had not gone along the road together. The tall man had gone first. The peasant woman had followed, since the point of her stick was sometimes to be seen inside the track of the tall man; while the short man had been the last on the road, his track now and then overlapping that of the peasant. Gross thought the tall man was a peasant by the formation of the shoe, and that the short person was a cavalry officer, as he had a tendency to turn in the toe as one does in the saddle.

Zenker used to say that the bare foot gave the most information. But Shauenstein maintained that the shod foot gave more signs of identity. He used to relate a case in his lectures in which it was known that an assassin had carried away the body of his victim, because of the changed manner in the line of march. But the particular thing about this case