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ween two vessels placed in observation at a distance apart of ten meters. After this, it was made to turn about so as to come back to its starting point. What makes this result the more remarkable is that the waters of the Bosphorus are disturbed by powerful currents that run in different directions, according to the place.--_L'Illustration_.

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PICTET'S HIGH SPEED BOAT.

It is now nearly a year ago since we announced to our readers the researches that had been undertaken by the learned physicist, Raoul Pictet, in order to demonstrate theoretically and practically the forms that are required for a fast-sailing vessel, and since we pointed out how great an interest is connected with the question, while at the same time promising to revert to the subject at some opportune moment. We shall now keep our promise by making known a work that Mr. Pictet has just published in the _Archives Physiques et Naturelles_, of Geneva, in which he gives the first results of his labors, and which we shall analyze rapidly, neglecting in doing so the somewhat dry mathematical part of the article.

For a given tonnage and identical tractive stresses, the greater or less sharpness of the fore and aft part of the keel allows boats to attain different speeds, the sharper lines corresponding to the highest speeds, but, in practice, considerably diminishing the weight of freight capable of being carried by the boat.

[Illustration: FIG. 1. PICTET'S HIGH SPEED BOAT.

A. Lateral View. B. Plan. C. Section of the boiler room. D. Section of the cabin.]

Mr. Pictet proposed the problem to himself in a different manner, and as follows:

Determine by analysis, and verify experimentally, what form of keel will allow of the quickest and most economical carriage of a given weight of merchandise on water.

We know that for a given transverse or midship section, the tractive stress necessary for the progression of the ship is proportional to the square of the velocity; and the motive

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