PROFESSOR THOMAS ON " VOLCANOES."

New Zealand Herald, Volume XX, Issue 6823, 29 September 1883, Page 5

PROFESSOR THOMAS ON " VOLCANOES."

■'~.- ■- -$ There was a very large attendance in the rooms of the Young Men's Christian Association yesterday evening, for the purpose of hearing Professor Thomas lecture on the above subject. Mr.. Fredk. Larkins occupied the chair. The lecture took the fonn of an oral explanation of a number of limelight views of volcanoes, active and extinct j also of volcanic strata at various places in and around Auckiand. The photographs of the local illustrations were taken by Mr. Josiah Martin, and tie limelight exhibition of them was in charge of Mir. Herbert Smith. Professor Thomas prefaced his discourse by saying that one could only judge of the past by the light of the present. Auck)j.r> presented the most interesting xemains bi extiuct volcanic action. The 'activity of these volcanoes dated from a time long before.the commencement of the historic. period." Nothing could be known directly and with.certainty, of the particular phenomena exhibited by each of these volcanoes. .One must be content by inferring what took place from thu phenomena exhibited by volcanoes active at the present time. [Views were exhibited of Vesuvius from various points of sight, also views of the main crater with its internal cones; also views of the crater and cones of Stromboli, of J'o'rullo in Mexico, together with views of lava "flows" and sections of craters. . The principal local views were those of the North Head and' I ' the cliffs between Cheltenham Beach, North Shore, and the lake.] In explaining the causes of volcanoes, Professor Thomas said the audience did not require to be told that the crust of the earth was solid; but if ■ *"person were to dig down deep it would be found, that the temperature increased as ha descended. -The old theory was that the centre of the earth was a molten fiery fluid. 'This theory had. been superseded, and the gerieral;opinion now was that the whole earth . Was'solid ; but intense heat, aided by im-» inense pressure, caused many of the rbeke ■which formed the earth's crust to melt, and ..the expansion which was the consequence produced'disturbance that manifested itself in;:fissures: upon the- surface,' sometimes radiating or ..'.'star shaped,", sometimes elon--'gated ;to..Ja^:great distance. , [Views were shbv?n : -.'of the manner in which these fissures' extended in various directions from; ■the;';:centre of activity. Viawu, were exhibited of Eangitoto,., of the Rotomahana aid other geysers.' The manner in. which the'form: of the volcanic cone was . illustrated'was very ingenious. A small . boiler with steam up. was placed under a • table, having an aperture, in the centre. Sand ; and ,V other earthy "materials of different , colours were placed under the aperture, and'" were_ thrown up by, the force of tbe steam, ■>. forming, a volcanic cone of the natural type;"' the materials thrown up at each '.' eruption "'.-'. depositing themselves in a stratified series. J \ This experiment elicited loud ; applause. The lecture .was'very interesting throughout,. On the motion of Dr.". Murray Moore a'vote, of thanks was accorded to the lecturer by ■acclamation; The Chairman complimented the_ committee of the Young Men'a. Christian Association on such an inter-, esting, series of lectures as those given by the Professors of the University College., ■He believed those gentlemen were desirous ■ to aid in improving the young men of Auckland.—Dr.. Purchas'said tha public had n& conception of the value of the lectures given.' by the Professors in connection with theTJnivereity. College. Those lectures were avoilable to tbe public on payment of a*>ery small fee for each sessional course. .. ■■;