DIURNAL BOTATION OF THE EARTH.

Daily Southern Cross, Volume XXVII, Issue 4406, 9 October 1871, Page 2

DIURNAL BOTATION OF THE EARTH.

On Friday night, in the Choral Hall, Mr. H. A. Severn delivered a lecture ou — " The daily rotation of the earth demonstrated to the eye by the celebrated experiment ' of Foucault, accompanied by explanations and illustrations of the earth's form, magnetism, &c." f lhe proceeds of the lecture were to be devoted towards the repauiug of St. Mary 'B Church, Parnell. At half-past seven o'clock, when the lecture was to commence, there was a moderately large mixed audience in the hall — there being a considerable sprinkling of ladies. On the motion of Dr. Mauusell, Major H,eaphy was voted to the chair. Is a few words, the Chairman introduced the lecturer. — Mr. Severn was very kindly received by the audience, and commenced by stating, that he was about to live here, and intended to deliver a series of popular lectures upon subjects which he named. He regretted the general apathy shown regarding scientific subjects in Auckland, and accounted for it by stating that there was a great want of apparatus wherewith to illustrate or demonstrate scientific truths, without which mere statements were- value- | less. He had paid a great deal of attention | to scientifio sabjects for the last 20 years, and at one time possessed an excellent set of apparatus, but takiug it into his head te go to JtTiji he had disposed of them, thinking there would be no use for them there. He had now changed his mind, and intended to live amongst a civilised people. The proceeds of the lectures he referred to would bo devoted to completing the purchase of a set of scientific apparatus. He enumerated the various instruments he had. He stated that the sun was distant from the earth 96,000,000 miles, and made a comparison between tw.o objects situated at the opposite ends uf the hall to illustrate the relative sizes of the earth and sun. He also exhibited a series of discs surrounding a central one, representing th* sun, showing I the various positions the earth occupied at different seasons of the year —in fact illustrating how the seasons were produced. He showed that of necessity the rotation of the earth was greater at the equator than at the poles, a&d that, were the velocity of the earth on its axis to be increased 154 times, human beinga and ail other things would fly from the surface into space. At the poles the motion was scarcely perceptible. The diameter of the earth along its axis from north to south waa 7,919 miles, and at tho equator about 16 miles more, so that the forth was not a sphere, but of a spheroidal form. This was illustrated by a simple experiment, and the causa of the protuberance at the equator and the Battening at the poles satisfactorily ex* plained. In the latitude of Auckland the rotary motion of the earth from west to east w.as about 1,000 miles per hour, and yet, to ordinary perceptions, ifc seemed as if the earth were quite stationery— an inert mass. At this part of his lecture he introduced the experiment of Foucault with the pendulum. The principle of the experiment is well known. Suspending a plumb-ball with a pendant point from a, high roof by a piece of very fin* vrire, and allowing it to oscillate freely, the natural law— that the plumb ball ! will keep in its own plane of oscillationcomes into operation where no magnetic attraction exists. By providing narrow ridges of flour laid upon a bar at right angles to its oscillation, and sufficiently near for the ball to strike them on each oscillation, the rotary motion of the earth soon becomes apparent; by the ridges of flour being cut away by the ball,one to the right and the other to the left. The success of the expe. riment was loudly applauded, as were many of the lecturer's domoaatratioas daring the course of the lecture. — Mr. Thomas Eussell moved a vote of thanks to the lecturer, which was seconded by Dr. MauoseH, and waa heartily accorded. A general ponTersation ensued between the lecturer and many of the audience, and several experiments were made while the audience was dispersing.