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Mr. Mallet travelled carefully over the shaken region during several months, and was afterwards employed for nearly two years in preparing his report, the title of which stands at the head of this article. This report was published in 1862, the Royal Society contributing three hundred pounds towards the expense. It fills two royal octavo volumes, and is most elaborately and beautifully illustrated, in a manner worthy of the first really thorough investigation in the department of Seismology.

It is hardly necessary to state that one investigation has not exhausted the subject; it has rather set the example of what ought to be done for many earthquakes; and it is especially of value, as leading the way in a new line of research, and as showing what can and must be done in order to arrive at as complete a knowledge as possible of the workings of the mysterious agencies by which these great convulsions are brought about. Some of the more important results obtained by Mr. Mallet in regard to the Neapolitan earthquake may here be given, as a specimen of the kind of material which will have to be accumulated from all quarters of the globe before the demands of scientific accuracy shall have been satisfied.

In the first place, in the map accompanying the report in question, the regions in which the shock was equally intense are designated by curves, called isoseismal curves; then the whole of the wave-paths, or lines of direction in which the shocks were propagated at each locality, are marked by red lines. These wave-paths of course radiate from the focal point of the shock, and so carefully were they determined, chiefly by observations of the position of fallen buildings, and the character of the movements and fractures in those left standing, that sixteen of these lines, when protracted back, pass through the same focal point, or within a circle of five hundred yards radius around it, while thirty-two more fall within a circle concentric with the former and of one mile radius. Now, theoretically, the intersection of any two wave-paths is sufficient to fix the position of the "seismic vertical," or the point on the earth's surface vertically above the spot where the impulse or shock originated. The evidence, then, in this case was ample for determining this point as accurately as possible; since, what

ever be the nature of the impulsive force, or however it may operate, the wave of impulse, as propagated outwardly, passes simultaneously, or almost so, from points about the actual focus at a considerable distance from each other, the point from which the disturbance starts not being, by any means, a mathematical one. The position of the point on the surface vertically over the seismic focus was found, as above, to be near Caggiano, a village sixty miles a little south of east from Naples.

The next important question to be settled was the depth of this focus below the surface, a point of great interest, as will be perceived at once, in its connection with the theory of earthquake action. This depth can easily be obtained by mathematical calculation, when the distance on the surface from any station to the seismic vertical is known, together with the angle of emergence of the wave-path, the seismic vertical being another wave-path, and the point of convergence of the two being the focus from which the wave started. Of course the limits of error are considerable in an investigation of this kind; but the results, as graphically exhibited on Mr. Mallet's diagram, are quite as satisfactory in their agreement as could be expected. Out of twenty-six separate wave-paths, twenty-three start from the seismic vertical at a depth of above 7 miles; the maximum depth is 81 miles, and the minimum 23 miles.* Eighteen of the wave-paths start from the seismic vertical within a vertical range of twelve thousand feet, and having a mean focal depth of 53 miles, which may be taken as the depth of the focus. Here is an extremely important numerical result, and similar results from other regions are highly desirable for comparison with this.

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It will be impossible here to enter into the detail of the other numerical results obtained by Mr. Mallet, the position and depth of the focal centre being, of course, the most important, and having been determined in this instance for the first time with any approach to accuracy. Other interesting points discussed in the summing up of the results of the investigation are the form of the isoseismal areas, — that is, of the regions over which the shock was felt with equal inten

*These results are given in geographical miles, of sixty to a degree.

sity; the relations of this area to the focal depth; the effects of the physical configuration of the surface and the geological structure of the region on the progress of the wave; the proofs of reflection and refraction of the shock by a range of mountains standing in the way, including reasons why certain areas escaped entirely; the form, position, and dimensions of the focal cavity; the amplitude and velocity of the wave, both on the surface and in the wave-paths; the velocity with which the shock started, and its gradual dying out; the relation of the seismic foci of the Italian Peninsula, and the general relations of the seismic bands of the Mediterranean basin. To give even a synopsis of the results obtained under the above heads will not be possible here; those who desire to investigate seismic phenomena must consult the volumes themselves.

We see that Mr. Mallet was fully justified in demanding more thoroughly scientific observations than those we had previously to his work, and that he has given a most excellent example of how such investigations should be made. He has shown that we can not only learn much from the application of seismological inquiries to future earthquake shocks, but that we have it in our power, to a certain degree, to recover the history of the past, by investigating the results of former convulsions as registered in the buildings fissured or in the ruins of those overthrown by ancient earthquakes.

Among the practical results of investigations like those of Mr. Mallet, there are none so interesting to the public at large, especially to persons living in earthquake regions, as those which relate to the proper methods of structure for safe houses and other edifices in countries liable to these disturbances.

This experienced observer expresses his strong conviction, "that the evils of the earthquake, like all others incident to man's estate, may be diminished, or even multiplied, by the exercise of his informed faculties and energies, and by his application of forethought and knowledge to subjugate this, as every other apparent evil of his estate, by skill and labor." He further adds, in reference to this important question: "Were understanding and skill applied to the future construction of houses and cities in Southern Italy, few, if any, human lives need ever again be lost by earthquakes, which there must recur, in their times and seasons."

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What is true of Southern Italy should also be true of the Pacific coast of our own territory, a region liable to severe shocks, and yet where we hope to see populous States. develop themselves in wealth, intelligence, and security to life. The prevailing tone in that region, at present, is that of assumed indifference to the dangers of earthquake calamities, the author of a voluminous work on California, recently published in San Francisco, even going so far as to speak of earthquakes as "harmless disturbances." But earthquakes are not to be "bluffed off." They will come, and will do a great deal of damage. The question is, How far can science mitigate the attendant evils, and thus do something towards giving that feeling of security which is necessary for the full development of that part of the country?

There has repeatedly been talk at San Francisco of establishing an astronomical observatory, either by itself or in connection with the State university. If the people of California are wise, and have money to give for scientific research, let them found a physical, and not an astronomical, observatory. We have enough of the latter already, ill-equipped, and in the majority of cases not manned at all. Quite a sufficient number of large telescopes are rusting on their piers in various parts of the country, as valueless for all real scientific results as if they never had been taken from the boxes in which they were imported. Let California take warning from these, and remember that a very large endowment is necessary for the permanent maintenance of an astronomical observatory, and that, if not permanently maintained, in the hands of an able astronomer, with the means of paying his assistants and of publishing his results, it will be nothing but an expensive toy. Besides, the climate of California and the climatological conditions are ill-suited to astronomical work in a fixed observatory. The fogs of San Francisco, and the dust of the interior, will be found alike unfavorable to the successful prosecution of this branch of scientific research. A physical observatory, on the contrary, which need not necessarily be a permanency, having as its principal object the investigation of the seismological phenomena occurring on the Pacific coast, would, if properly managed, furnish results of exceeding value, not only NO. 223. 39

VOL. CVIII.·

as contributions to an important branch of science hitherto much neglected, but as having a practical bearing on the welfare of the people and the development of the State, the value of which can hardly be overestimated. In no portion of the world is there a better chance for an establishment having in view the thorough investigation of earthquake phenomena. The great plain of the Sacramento and the San Joaquin should for a time be connected with San Francisco galvanically, by wires proceeding from the branch observatories at properly selected localities. Seismometers of the most approved construction should be set up, and their records compared with the other results of every important shock, as shown in the effect on buildings and on the surface of the ground, and in all the other methods of which Mr. Mallet's book furnishes so excellent a model.

Of Herr Volger's volume and theory something may be said at another time, in discussing the various theories of the nature of the forces involved in the phenomena of volcanoes and earthquakes. J. D. WHITNEY.

ART. VIII. THE SESSION.

THERE is much reason to regret that every voter in the United States cannot be compelled, at some period of his life, to visit Washington, for the purpose of obtaining the passage, through the various stages of legislation, of some little bill, interesting only to himself, and perhaps having "a little money in it." The lesson would be a useful one. As the visitor cast from the lobby a momentary glance through the swinging doors of the House, and was bewildered by the crash and war of jealous and hostile interests within, as he felt how his own just and proper request was the sport of a thousand accidents, as he appreciated the difficulties in the way of getting a committee to report his bill at all, and the still greater difficulty of putting it on its passage, and as he then watched it float here and there in the eddying current of legis

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