One of the most interesting places in Washington at this particular timeis the earthquake or seismographic division of the U. S. weather bureau. There, in charge of Prof. C. F. Marvin, earthquake specialist and meteorologist, are kept the delicate machines known as seismographs, which record the time and intensity of any quake that may happen to pass this way, as well as a mass of data referring to earthquakes volcanic eruptions and other causes of disaster to humanity.

The Seismograph Records Time And Intensity Of Eart 170

On one of the weather bureau seismographs was made a complete record of the great earth wave which brought death and ruin to the fair city of San Francisco.

The delicate needle of the seismograph had been tracing long, straight white lines on the gelatined surface of the record sheet Wednesday morning, when it suddenly became agitated at 8 o'clock .10 and 20 seconds, and began to make more or less elongated waves. At 8.25 o'clock the strong waves began, and the recording needle moved rapidly back and forth across the sheet. Then followed the most violent waves between 8.32 and 8.35 o'clock, 75th meridian time, as is shown by the record.

At one time the motion of the needle was so vigorous that its point went off the sheet, which is kept in motion by a clock machine, and the point did not return to the sheet until there was a secondary lull in the great disturbance. Then, when the needle had resumed its tracings, the earth vibrations and waves continued until 12.35, when the agitations ceased.

Each of the lines on the record sheet represents an hour of time, the movement of the sheet keeping time with the tick of the connected clock. The units of time are marked on this sheet, which is covered with gelatine, and thus the observer is enabled to tell just when the earthquakes began and when they ended by the markings made by the needle point.

The atmosphere which Prof. Willis L. Moore, chief of the weather bureau, has installed in his department is said to be one of the best in the world. It is installed in a basement apartment away under the weather bureau building, far removed from the noisy hurly-burly of the streets, and is practically a mechanical recluse, only Prof. Marvin and the immediate observers being allowed to invade the sanctity of its subterranean home.

For purposes of exhibition and explanation a duplicate seismograph has been set up in a room adjoining the office of Prof. Marvin. This instrument has been shown and described to a large number of visitors since the San Francisco disaster.

Its Extreme Sensitiveness

The extreme sensitiveness of the seismograph is shown in the following statement made by Prof. Marvin:

"The extreme sensitiveness to tilting is exhibited in several ways. The weight of the observer almost anywhere on the floor of the small room in which the instrument is installed suffices to tilt the pendulum enough to show on the record; a large displacement is produced by standing at one side of the pedestal. It has been noticed also that the weight of an ice wagon which stops daily to deliver ice at a basement entrance to a building causes a definite displacement of the trace of about one millimeter, which disappears when the wagon drives away.

There are no vibrations or oscillations registered, only a distinct elastic bending of the ground due to the load. This motion, moreover, is communicated through the foundation walls of the building. The distance of the wagon from the seismograph is about 20 feet; the asphalted drive and the basement floor are on the same level. The subsoil is a hard clay.

Its Extreme Sensitiveness 171

The earthquake wave recorded at such a long distance from the real seat of trouble, was in the nature of a long, regular motion like a sea wave. The motion at San Francisco was quick and sudden, and therefore very destructive.

This violent agitation produced destructive strains, with the tendancy to shake buildings to pieces, whereas at a distance where the movement of the earth is slow and regular all portions of the building may follow the motion of the ground.

Prof. Marvin said, in illustration, that the passing of a rapidly moving railroad train produces a vibration of the earth similar to that produced at the place where an earthquake is causing destruction, only in greatly reduced magnitude.

Unwritten Earthquake History

The professor gave the reporter a piece of unwritten earthquake history of recent origin and local application. He said that at 4.35 o'clock p. m. of April 10 - eight days before the San Francisco visitation - a rather severe shock of earthquake was recorded on the weather bureau seismograph. Up to this time, however, nothing has been heard from the mysterious quake or its effects.

On another recent night three distinct shocks were recorded, but they remain unidentified as to effects, and it is not known whether the quakes occurred out at sea, or where. An earthquake was reported from Formosa on April 14, but it has not been connected with the mysterious quakes recorded at the weather bureau.