Page:Popular Science Monthly Volume 2.djvu/765

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Prof. Henry was married in May, 1830, to Miss Alexander, of Schenectady, the sister of Prof. Alexander, of Princeton, and from the ardent devotion of his wife, and the fraternal sympathy of her brother in his pursuits, he has received assistance and support beyond that which usually fall to the lot of men. The most peaceful, and to himself the most profitable, part of his life was that spent in Princeton, for which place, and the college connected with it, he retains the warmest attachment.

The following is a brief enumeration of his scientific investigations and discoveries:

1. A sketch of the topography of the State of New York, embodying the results of the survey before mentioned.

2. In connection with Dr. Beck and the Hon. Simeon De Witt, the organization of the meteorological system of the State of New York.

3. The development, for the first time, of magnetic power, sufficient to sustain tons in weight, in soft iron, by a comparatively feeble galvanic current.

4. The first application of electro-magnetism as a power, to produce continued motion in a machine.

5. An exposition of the method by which electro-magnetism might be employed in transmitting power to a distance, and the demonstration of the practicability of an electro-magnetic telegraph, which, without these discoveries, was impossible.

6. The discovery of the induction of an electrical current in a long wire upon itself, or the means of increasing the intensity of a current by the use of a spiral conductor.

7. The method of inducing a current of quantity from one of intensity, and vice versa.

8. The discovery of currents of induction of different orders, and of the neutralization of the induction by the interposition of plates of metal.

The discovery that the discharge of a Leyden jar consists of a series of oscillations backward and forward until equilibrium is restored.

10. The induction of a current of electricity from lightning at a great distance, and proof that the discharge from a thunder-cloud also consists of a series of oscillations.

11. The oscillating condition of a lightning-rod while transmitting a discharge of electricity from the clouds causing it, though in perfect connection with the earth, to emit sparks of sufficient intensity to ignite combustible substances.

12. Investigations on molecular attraction, as exhibited in liquids, and in yielding and rigid solids, and an exposition of the theory of soap-bubbles. (These originated from his being called upon to investigate the causes of the bursting of the great gun on the United States steamer Princeton.)