August 15, 1884] 



SCIENCE. 



135 



The door in the middle of this southern wall 

 on the main floor opens into a large closet, a 

 store-room for glassware. The remaining door 

 leads to a set of smaller rooms under the gallery 

 of the lecture-room, intended for special work, 

 and to be more fully fitted up at some future 

 time, or as the needs of investigation shall 

 make desirable. 



Under the seats and openings into two of 

 these small rooms are closets, dotted in the 

 plan, which are convenient places for storage. 

 The first of these rooms is known as the 

 1 weighing- room.' It contains a delicate bal- 

 ance (Bl) on a firm shelf, and a Wiedemann's 

 galvanometer (Gm) fixed on a pier near the 

 door. The telescope (77) of the latter is 

 attached to a column in the centre of the 

 room. In the corner is a small refrigerator 

 (H) with a waste-pipe. This room, as well 

 as its neighbors, has water, gas, and wires 

 from the tower. The next, or ' dark room,' 

 has no windows, and is intended for optical 

 experiments, or for any work requiring the 

 exclusion or perfect control of daylight. A 

 shutter near the door to the south permits any 

 arrangement of diaphragms and lenses which 

 can possibly be called for. At some future 

 time a Thomson galvanometer will be set up 

 in this room. 



The corner room, known as the ' light-room,' 

 has no special purpose, but is to be used for 

 such work as may require a veiy good light 

 and perfect quiet. The position of this room, 

 in the corner of the building farthest removed 

 from the streets, is very favorable for uninter- 

 rupted, quiet investigation. In one corner is 

 the ' photograph-room ' for the preparation 

 and development of the plates. Against the 

 wall, in the opposite corner, a pendulum nryo- 

 graph (PM) is fastened permanently in posi- 

 tion, and covered by a dust-proof case. This 

 is the instrument made by Dr. J. J. Put- 

 nam, and described by him in the Journal 

 of physiology (ii. p. 206). Wires run from 

 this apparatus to the adjoining closet, — an 

 arrangement that is found convenient for 

 experiments with reaction time. One of 

 the southern windows of the light-room has 

 also a broad heliostat shelf (BS) outside, 

 so that a beam of light may be sent even 

 into the assistant's room, or, b} T a suitable 

 disposition of mirrors, into any part of any 

 other room. The remaining door of the 

 light-room opens upon a passage-way which 

 leads to the chemical laboratories, and 

 makes the departments independent of the 

 main hall or the lecture-room for communi- 

 cation. 



KRAKATOA. 



The more the information accumulates with re- 

 gard to the eruption of Krakatoa on Aug. 27, 1883, 

 the more this phenomenon proves to have been re- 

 markable and unique as a series of violent explosions. 



From Nature of July 17 we learn, that, at the meet- 

 ing of the Meteorological society of Mauritius on 

 May 22, several interesting communications were 

 made with regard to this eruption; among others, a 

 letter from a M. Lecomte, dated at Diego Garcia 

 (latitude 7° 20' south, longitude 72° 35' east of 

 Greenwich) on April 24, describing how at breakfast, 

 on the morning of Aug. 27, they had heard detona- 

 tions, low but violent, and, attributing them to a 

 vessel in distress, had run, and had sent men, to dif- 

 ferent points of the shore of the island, who were 

 unable to see anything to cause such sounds; also 

 how the captain and mate of the Eva Joshua, just 

 leaving Pointe de l'Est to anchor at Pointe Marianne 

 (these places I cannot find, but suppose, from the 

 account, that they are near Diego Garcia), had heard 

 the same detonations, and sent men to the mast- 

 heads, without seeing any thing. These, with the 

 previous reports from Rodriguez, showed that in three 

 distinct cases the sounds of the Krakatoa explosions 

 were plainly heard at distances of at least twenty- 

 two hundred miles, and, in the case of Rodriguez, of 

 nearly three thousand. 



It will be remembered, that in Nature, May 1, it was 

 stated by Herr R. D. M. Verbeek that these sounds 

 were heard in Ceylon, Burmah, Manila, New Guinea, 

 and at Perth on the west coast of Australia, and, in 

 fact, at all places within a radius of about 30°, or 

 two thousand miles. But these later reports from 

 Rodriguez and Diego Garcia show, that across the 

 waters of the Indian Ocean, with no land interven- 

 ing, they were carried distinctly to much greater dis- 

 tances. 



The still more remarkable atmospheric gravity- 

 waves which travelled round and round the globe in 

 all directions from the Straits of Sunda, and which 

 were fortunately registered on the self-recording 

 pressure-guage of the large gasometer at Batavia, 

 close by Krakatoa, were also registered on the baro- 

 grams at Mauritius; and here there were distinctly 

 recorded four successive transits of the waves from 

 east to west, and three from west to east, the same 

 as shown by Gen. Strachey to have occurred at some 

 of the European stations. But, what is still more 

 remarkable, there is a faint trace of a fifth transit 

 of the waves from east to west on the morning of 

 Sept. 2; i.e., more than six days after the explosions, 

 and when the waves had travelled more than four 

 times round the earth, or about a hundred and two 

 thousand miles. The most sensitive barograph at 

 the signal-office in Washington also shows small 

 waves, which are probably the record, also, of this 

 fifth transit (and barely possibly of the succeeding 

 sixth transit of the same): but the phenomena at 

 Washington are complicated by the fact that it is 

 witliin about 33° of the antipodes of Krakatoa, and 

 that the waves have different velocities east and west, 



