With instruments analogous to these, observations have been made by various observers in all portions of Italy, extending over a period of ten years. Every precaution appears to have been taken to avoid accidental disturbances, and the experiments have been repeated in a variety of forms. _Results obtained in Italy._—The results which from time to time have been announced are of the greatest interest to those who study the physics of the earth’s crust, and they appear to be leading to the establishment of laws of scientific value. It would seem that the soil of Italy is in incessant movement, there being periods of excessive activity usually lasting about ten days. Such periods are called seismic storms. These storms are separated by periods of relative calm. These storms have their greater regularity in winter, and sharp maximums are to be observed in spring and autumn. In the midst of such a period or at its end there is usually an earthquake. Usually these storms are closely related to barometric depressions. To distinguish these movements from those which occur under high pressure, the latter are called baro seismic movements, and the former _vulcano seismic_ movements. The relation of these storms to barometric fluctuation has been observed to have been very marked during the time of a volcanic eruption. At the commencement of a storm the motions are usually small, and one storm, lasting two or three days, may be joined to another storm. In such a case the action may be a local one. It has been observed that a barometrical depression tended to bring a storm to a maximum, whilst an increase of pressure would cause it to disappear. Sometimes these actions are purely local, but at other times they may affect a considerable tract of land. If a number of pendulums of different length are observed at the same place, there is a general similarity in their movements, but it is also evident that the free period of the pendulum more or less disturbs the character of the record. The greatest amplitude of motion in a set of pendulums is not reached simultaneously by all the pendulums, and at every disturbance the movement of one will predominate. From this Rossi argues that the character of the microseismical motions is not constant. Bertelli observed that the direction of oscillation of the pendulums is different at different places, but each place will have its particular direction dependent upon the direction of valleys and chains of mountains in the neighbourhood. Rossi shows that the directions of movement are perpendicular to the direction of lines of faults, the lips of these fractures rising and falling, and producing two sets of waves, one set parallel to the line of fracture, and the other perpendicular to such a direction. These movements, according to Bertelli, have no connection with the wind, rain, change of temperature, and atmospheric electricity. [Illustration: FIG. 38.]