May, 1911. 



KNOWLllDGE. 



197 



to the masses of the particles constituting the rays. Further- 

 more, the velocity of the rays is so great that the production 

 of particles not completely stable under ordinary circum- 

 stances are enregistered on the plate. 



Professor Sir J. J. Thomson has been able to obtain 

 evidence of the momentary existence of CHi, CH>, and CHi. 

 Furthermore one gas does not necessarily give rise to only one 

 type of ray, but one parabolic arc may be due to the atom 

 with two positive charges (^o /• another to the atoin with a 

 negative charge (5) or a positive charge (q), another to the 

 molecule (o.,), another to a more complicated molecule (o,)- 

 or more complicated still (cjj). It appears that a negatively 

 ch;irged molecule is not obtainable easily, because in the 

 molecule the electrons are more firmly bound and held together 

 by their nnitual influence, whereas in the atom they are freer ; 

 consequently, when a collision occurs with a negative corpuscle, 

 the latter may attach itself to the atom but not so easily to the 

 molecule. Sir Joseph Thomson illustrated this point in his 

 lecture by recourse to a simple experiment with magnets. 

 Compass needles were balanced on points on a card, suspended 

 from the roof, which hung close to a magnet. When the 

 compass needles were free to move, the whole card was 

 attracted by the magnet : when the compass needles were 

 removed and laid at random on the card, the latter was not 

 attracted to the same extent. 



This new method of analysis, by means of high vacuum 

 discharges, will be excessively valuable in investigating the 

 charges which more complicated atoms undergo and will 

 no doubt lead to many new discoveries and unlock the 

 secrets of the atom. Strange lines appear in these spectra 

 which are not readily explainable. 



{c.}>. 65 possible """h, ) 



ACTIVE NITROGEN.— Professor R.J. Strutt delivered the 

 Bakerian Lecture on April 6th to the Royal Society. The 

 subject of his lecture was the afterglow from the passage of 

 the electric discharge through nitrogen. We mentioned it in 

 the Physics Notes for February. If pure nitrogen be passed 

 through a discharge tube continuously at a low pressure by 

 suction with a Grede pump, on leaving the discharge tube, it 

 glows with a yellow light and is highly active. It combines 

 with iodine causing the latter to glow brilliant blue, gives a 

 compound with phosphorus — that which is no doubt produced 

 during the exhaustion of Sir OUver Lodge's high tension 

 valves by means of phosphorus — and causes the metals, 

 when warmed sufficiently to give off vapour, to emit light 

 giving their characteristic line spectra. Professor Strutt 

 illustrated this point in a most beautiful manner by showing 

 the green glow emitted by a small piece of thallium placed in 

 the tube through which the active nitrogen passed. Professor 

 Strutt considers the nitrogen to be in the atomic form. 



SEISMOLOGY. 



By Charles Davison, Sc.D., F.G.S. 



THE RECENT ERUPTION OF TAAL VOLCANO 

 IN THE PHILIPPINE ISLANDS.— In the island of Luzon, 

 nearly forty miles south of Manila, lies lake Bombon. Near 

 the centre of this lake, from Volcano Island, there rises Taal 

 \'olcano. which, by its eruption last January 30th, caused so 

 nmch damage to the surrounding villages. The crater walls 

 vary in height. At no point are they lower than four hundred 

 and ninety-two feet, at the highest they rise to nine hundred 

 and ninety-six feet. 



When the United States Government took over the Philippine 

 Islands at the close of the last century, they acquired the 

 services of a Jesuit priest, the Rev. M. Saderra Maso, who for 

 many years had studied and published valuable reports on the 

 earthquakes and volcanoes of that unstable group of islands. 

 Being appointed an assistant-director of the U.S. Weather 

 Bureau. Father Saderra Maso has continued his useful 

 work, one of the latest results of which is the investigation 

 of the recent eruption of Taal Volcano. Of his interesting 



report on this eruption a summary ii given in the present note. 

 During the night of January 27th-2Sfn, the volcano issued the 

 first warnings of the coming eruptio:"-. Instead of the usual 

 clouds of white steam, great puffs of biack smoke were emitted 

 from the main crater, accompanied by rumbling sounds and 

 tremors. On January 28th and 29th, explosions and earthquakes 

 became more frequent and stronger, until at about 2.20 a.m., 

 on January 30th, they culminated in a tremendous explosion, 

 the sound of which is said to have been heard at a distance of 

 two hundred and fifty miles. .A huge black cloud rose from 



FiciRi: 1. 



the crater, lit up by flashes of lightning, vivid sparks and 

 bursting globes of fire. .A heavy fall of boiling mud followed 

 the explosion, and destroyed all the vegetation and the flimsy 

 houses on Volcano Island and along the western and north- 

 western shores of the lake to a distance of ten miles from the 

 crater, and caused the death of between one thousand two 

 hundred and fifty and one thousand three hundred of their 

 inhabitants. On the accompanying sketch-map. reproduced 

 from Father Saderra Maso's report, the black dots indicate 

 the towns and villages that were obliterated, and the small 

 crosses those that were damaged. 



After the eruption, there was a rush of air towards the 

 volcano, which was noticeable for many miles around. 

 Barometers registered a rapid fall of atmospheric pressure, 

 which at Batangas (seventeen miles from the volcano) 

 amounted to about one-twelfth of an inch, and at Manila 

 (thirty-nine miles) to one-twenty-fiffh of an inch. 



The distribution of the volcanic mud was governed by the 

 direction of the prevailing wind, which was from the south- 

 east. On Volcano Island and the western and north-western 

 shores of the lake, the mud formed a layer from two to three 

 feet in thickness. With increasing distance, its thickness 

 gradually diminished, until beyond a distance of fifteen miles 

 only grey gritty dust was deposited. The finer dust was, of 

 course, carried still farther, and, on the morning after the 

 eruption, some fell at Manila. On the south-eastern shore 

 of the lake no mud was to be seen, and only a little was 

 deposited on the eastern and north-eastern shores. 



.Vfter the great eruption of January 30th, no other outlim>-t 

 of anv importance took place, and the earth(]uake-shocks soon 

 diminished both in frequency and strength until they prac- 

 tically ceased on February 7th. 



Along the shores of the lake, the damage was increased by 



