Page:Popular Science Monthly Volume 2.djvu/647

Rh visible to the audience by means of the vertical lantern, so that the processes of demagnetizing, with all the interesting motions of the needles, were seen projected on a luminous screen, eighteen feet in diameter.

"The lecture itself is a masterly production, and exhibits the result of much close reading as well as experimental research. Quotations are given from earlier writers on magnetism, illustrative of the sound knowledge which they possessed; and, as each experiment illustrative of the lecture is described, as well as the apparatus employed in manipulation, the reader is conducted from a consideration of the most ordinary magnetic phenomena presented by bar and electro-magnets to that of the same phenomena evolved from terrestrial magnetism. A paragraph selected from the closing portion of the lecture will fully substantiate this statement: 'Now we have finished our experiments; and what have they shown? I have temporarily magnetized a bar of soft iron, by pointing it toward a pole of our large magnet. I did the same with the bar and the earth. I permanently magnetized an iron bar by directing its length toward the pole of the magnet, and vibrating it with a blow of a hammer. I did the same with a bar, struck when pointed toward the earth's magnetic pole. I have shown you the action of a small magnetic disk on iron filings placed above and around it. You saw the earth produced the same action on the beams of the aurora. I showed you the action of this disk on a freely-suspended magnetic needle, and pointed out to you the earth's similar action on a dipping-needle carried over its surface. I have evolved a current of electricity from a magnet, by cutting with a closed conductor across those lines in which a magnetic needle, freely suspended, places its length. I did the same with the earth by cutting across those lines which are marked out by the pointing of the dipping-needle. Therefore, what am I authorized to infer? When the effects are the same, the causes must be the same; for, according to all the principles of philosophy, and conformably to that universal experience which we call common-sense, like causes produce like effects.'"

is a valuable monograph upon an important subject, and is an interesting indication both of the progress in medical science, and of the need and possibility of diffusing its benefits among the people. More and more as physiology and pathology advance, are we discerning the fundamental nature of the thermal processes in the living economy. That the animal body is, first of all, a furnace to which the digestive system furnishes fuel, and the respiratory system the agent of combustion, is not a mere curious chemical fact, but it is a central and vital physiological law, which is involved with the whole subject of health and disease, of life and death. It may not be proper to say that heat is life, but it is an essential condition of it, and is unquestionably the raw material of it—if not life, it is yet transformable into life. But the organism generates its heat and loses it by fixed physical laws, while the whole scheme of its activities depends upon the maintenance of the vital temperature at a given point, the norme of health, which is 98° Fahr. in the Caucasian race. Any deviation from this point is an indication of disturbance and disease. The rise of temperature above the standard involves one class of disturbances; its fall below, another class. The physician alone can deal with the special complications which arise when the temperature ascends or sinks abnormally, but it is in the power of those not physicians to observe the indications, and thus to determine not only when the medical man should be called, but to furnish him with positive and valuable data for his treatment. The use of the thermometer has become indispensable in intelligent medical practice, but Dr. Seguin has shown that it is equally indispensable to mothers in the intelligent management of their children. The only difficulty is to get them to use it, and to give a little attention to the method of registering the results observed. The ordinary thermometer is badly graduated with reference to this use, and so Dr. Seguin has devised a physiological thermometer marked in so simple a way that it may be employed by anybody