438 



NA TURE 



[March 7. 1895 



The following are short summaries of each case : 



S.s. FaraJay. — The wave was visible like a line of high 

 land on the horizon about five minutes before ii struck the 

 vessel. 



S.s. IfisftrnJtind. — A huge wave rose to a great height just 

 in advance of the ship. No other similar waves were raft with. 

 About noon the wind had changed from S. W. to W.N.W. 



S.s. Gtrmanic. — Wind \V. X. \V. with terrific squalls. Shipped 

 a tremendous sea over bow. 



^■.r. Umlria. — The disturbance came from ^N.W. and con- 

 sisted of iwo waves. The first one was broken, the second one 

 green. The wind had previously changed from S.W. to N.W. 



H.M.S. Oronlcs. — While steaming in smooth water a huge 

 wave broke over the vessel forward. 



6. Festina Ltnte. — A sleep sea fell on board from both sides. 



S.s. .\tanhattan. The sea was high, but fairly true until a 

 mountainous wave broke on board from N.W. 



S.s. Diamond. — L)ing to, awaiting daylight to enter port. 

 The wave was heard some lime before it was seen, and then 

 seemed lo be about 40 feet high. The vessel never rose to it, 

 but was literally submerged for a time. 



An examination of the chart will show that with the excep- 

 tion of the U'lilernland each wave may have originated at a 

 common centre, and might therefore be due to subaqueous vol- 

 canic aciivily. However, as the solitary waves which strike 

 the west coast of South America and the so-calUd Death Waves 

 on the west coast of Ireland are said to be regarded as pre- 

 cursors of storms, it is possible that these solitary Atlantic waves 

 may be due to a similar cause ; but even llien it is inexplicable 

 how a number of comparatively small and regular waves can 

 be convened into one abnormal one, or how the reported 

 changes of wind and consequent confused sea could 

 produce such a wave. It will be noticed that the 

 dates for the Festina Lentt, Manhattan, and Diavioiid arc 

 very close together, and therefore there is a possibility that they 

 were struck by (he same wave. C. E. Stromeyer. 



Glasgow, February 18. 



The Presence of a Stridulating Organ in a Spider. 



Whilst spending a short time at Alice Springs, in Central 

 Australia, during the course of last year, in connection with the 

 Horn Scieniific Expedition, I found that it was firmly believed 

 by a considerable number of people, while men and natives 

 alike, that a spider existed in Cenlral Australia which made a 

 booming noise at night. Thanks to the assistance of the blacks, 

 the spider itself was easily captured, but I could detect no organ 

 capable of producing a booming sound. The animal forms a 

 tubular burrow, about three-quarters of, or an inch, in diameter, 

 which passes down for some eighteen to twenlyfour inches in 

 a slightly slanting direction unlil it terminates in a small 

 chamber capable of holding the animal comfortably. In this 

 chamber arc found fragments of beetles upon which the animal 

 has preyed, and a certain amount i>f web material ; but there is 

 no regular lining to the tube or chamber. The spider, which 

 may reach a length of two and a half inches, and a span across 

 the legs of five inches, proves to be J'/irictis crassipcs, belong- 

 ing lo the tribe Tcrrilelariir, to which also belongs the well- 

 known Afygale. 



After li-iiening carefully for the noise, and spending with a 

 friend a night out in the open, in a spot where the booming could 

 be heard, we came to the conclusion th.at the noise attributed lo 

 the spider was, in reality, made by a quail. 



However, we kept some dozen specimens under observation 

 in tin and wooden boxes, and after a few days in captivity, 

 during which time they were very slugi;ish, one or two of them 

 began to be more .active, and on irritating one of the livelier 

 ones (a Urge female) with a straw, I was pleased to see her 

 rise on her hinder legs, and lo hear her make a low whistling 

 noise, moving alternately the paljjs up and down on the chcli- 

 cetx as she did so. Whilst doing this she would make short 

 angry darts al the straw. 



On examination it was seen that the surface of the basal 

 joint of the palp was provided with a somewhat ovalshapcd 

 comb-like structure co'npoied of hard chitinous rods of various 

 lengths, each enlinj in a club-shaped head. The comb is so 

 placed that when the palp is moved up and down it rubs against 

 a special part of the chelicera, which is provided with several 

 rows of strong, sharply-tapering spines, and Ihe sound produced 



NO. 1323. VOL. 51] 



can be heard, when the spider is in a box in a quiet room, at a 

 distance of, at any rate, six or eight feet. 



I was not at the time aware of the fact that, in the Tiansa.ti^'N! 

 of the Entomological Society for 1S77, Mr. Wood Mason had 

 described a very similar stridulaling organ in another ground- 

 spider, M)\^,i!e stridulans, and it is interesting to note the close 

 resemblance between, as well as the presence of, the oi^ans in 

 these two genera, both of which belong 10 the tribe Terrilelaria. 

 The figure given by Mr. Wood Mason admirably illustr.ites the 

 position of the spider when it stridulates. 



I hope to publish a full description of the organ in the volume 

 dealing with the work of the Horn Expedition. 



Balpwin Spencer. 



Biological Laboratory, Melbourne University, 

 January 24. 



The Spectrum Top. 



PerhaI'3 some of your readers may be glad to learn that the 

 curious phenomena of the spectrum top can be shown on a 

 screen lo a large audience. It is only necessary to paint the 

 usual black lines and sector on a suitable disc of glass, and 

 then lo mount it in a revolving stage which can be rotated in a 

 lantern by means of a multiplying wheel. The projected disc 

 of light must not be too large ; if the lime-light be used the disc 

 may be about 2 feel in diameter, and about double that 

 size with the electric arc. A great variety of elTects can be 

 obtained by interposing coloured glasses in the path of the 

 beam ; e.g. with a green glass, and in diffused gas-light, the 

 dark sector and lines appear to be niauve-coloured when 

 suddenly stopped after rapid rotation, or when very slowly 

 rotated, but become of a dark blue when the gas is turned off. 

 On rotating the disc in the usual way the lines appear to be 

 blue, green, and violet. 



With a blue glass in gaslight the dark sector and lines 

 appear to be yellow when suddenly stopped, but a fine purple 

 without diffused light. The colours given by tlie lines at a 

 moderate rate of rotation are red, grey, green, and blue. With 

 a monochromatic red glass, the lines appear lo be blue, grey, 

 red, and dark red. 



Is it not somewhat extraordinary that a rich blue colour can 

 be obtained when dealing only with monochromatic red light ? 

 With whatever coloured light the disc is fed, the characteristic 

 red lines at the centre, and blue .at the periphery, or .- /<v lersa, 

 seem almost invariably to appear. AUogelher the phenomenon is 

 worthy of further 'study by physiologists and physicists ; the 

 lantern appears to throw, in a double sense, new light upon this 

 interesting problem. The idea of employing transmitted 

 instead of reflected light for producing the phenomena of the 

 spectrum top is partly the suggestion of Mr. T. J. Walls, 

 instrument maker, Edinburgh, who constructed the disc for 

 me. Dawso.n Turner. 



Edinburgh, March 4. 



THE AGE OF THE EARTH. 



PROF. PERRY and I had not to wait long after the 

 publication of his article " On the Age of the ICarth " 

 (Natukk, January 3, 1895, pp. 224-227) to learn that 

 there was no ground for the assumption of greater con- 

 ductivity of rock at higher temperatures, on which 

 his effort to find that the consolidation of the earth took 

 place far earlier than 400 million years ago, is chiefly 

 founded. In a letter of date January 13, most coiirie- 

 ously written to me by Dr. Robert Weber in conseipience 

 of his having seen by my letter to I'rof. I'erry of 

 December 13, that we were anxious to find how far his 

 experimental results regarding dillerenccs of thermal 

 conductivity and specific heat at dillerent temperatures 

 could be accepted as trustworthy, he tells me that he had 

 made farther experiments on an improved plan, and that 

 on the whole his investigations do not seem to prove 

 augmentation of conductivity with temperature : and he 

 kindly gives me, with permission to communicate lo 

 NAitKijthe following results, hitherto unpublishetl, of 

 experiments which he made in t e years 18S5 and 1S86 



