302 



NATURE 



[ 



of iSoo fathoms, in the South Atlantic (S. lat. 46° l5', E. long. 

 48* 27'), a living specimen of a magnificent shell belonging to 

 Cymbitim, or an allied genus, wliich is 6| inches long and 4 

 inches broad ! I dredged other Mollusca from an inch and a 

 half to nearly double that length in the /'i)rrt<//«t' and Tahvous 

 expeditions. Willemcies Suhm mentions among the Challtit^cr 

 discoveries a gigantic crustacean or sea-spider from 1375 fathoms, 

 which measured nearly two feet across the legs. 



Sir Wyville Thomson gives an eloquent description of life in 

 the deep sea, when he says that the latter "is inhabited by a 

 fauna more rich and varied on account of the enormous extent of 

 the area, and with the organisms in many cases apparently even 

 more elaborately and delicately formed, and more exquisitely 

 beautiful in their .•■oft shades of colouring, and in the rainbow 

 tints of their wonderful phosphorescence, than the fauna of the 

 well-known belt of shallow water teeming with innumerable 

 invertebrate forms which fringes the land. And the forms of 

 these hitherto unknown living beings, and their mode of life, 

 and their relations to other organisms whether living or extinct, 

 and the phenomena and laws of their geographical distribution, 

 must be worked out." 



It was formerly supposed that animals could not exist at great 

 depths because of the great pressure to which they were sub- 

 jected. Mr. Moseley says ' "the pressure exerted by the water 

 at great depths is enormous, and almost beyond comprehension. 

 It amounts roughly to a ton weight on the square inch for every 

 1000 fathoms of depth ; so that, at the depth of 2500 fathoms, 

 there is a pressure of two tors and a half per square incli of 

 surface, which may be contra^ted with the fifteen pounds |ier 

 square inch pressure to which we are accustomed at the level of 

 the sea." But it must be recollected that water is nearly incom- 

 pressible, and that marine animals which are surrounded by such 

 a fluid, and are to a certain extent filled with it, would not 

 necessarily be inconvenienced by the superincumbent weight. 



Animals from great or even from what may be considered 

 moderate depths are always brought up dead, the cause of death 

 being unknown. This is another problem worthy of being 

 worked out. 



The migration or distribution of marine animals throughout 

 the open sea is quite free, and is unobstructed only by great or 

 abrupt changes of level in the bed of the ocean, which operate 

 as barriers. Even animals of a fixed or sedentary nature in tlieir 

 earliest state of grow th swim on the surface, and are therefore 

 unchecked in their onward course by any submarine barrier. 



The doubt whether any life exists in the inteimediate space or 

 zone which lies between that of the surface and that of the 

 bottom of the dee|) sea has now, I believe, been set at rest. 

 The naturalists in the Josephine expedition believed that this 

 intermediate zone is lifeless; and Sir Wyville Thomson seems 

 to have been of the same opinion. The towiig-net adopted by 

 Mr. Murray in the Challenger expedition for such researches w as 

 to some extent successful ; but Capt. Sigsbee, of the U.S. Coast- 

 Survey steamer Blakc, invented a cylinder or machine, calkd the 

 "gravitating trap," which completely answered the purpose of 

 collecting at any particular depth the animals which occurred 

 there. Prof. Alexander Agassiz, in his communication to the 

 Superintendent of the Survey made last August, and no«- pub- 

 lished, records the experiments thus made, and says that they 

 "appear to prove conclusively that the surface-fauna of the sea 

 is really limited to a comparatively narrow belt in depth, and 

 that there is no intermediate belt, so to s^eak, of animal life 

 between those living on the bottom, or close to it, and the 

 surface pelagic fauna." 



I am not aware that any deep-sea animals adopt or avail 

 themselven of the same means that oceanic or land animals use 

 for purposes of protection and concealment, chiefly by colora- 

 tion or by what has been termed " mimicry." Many cases of this 

 kind are known to occur in birds, fishes, mollusks, Salpii, insects, 

 crabs, shrimps, and worms. 



None of the animals whoje remains are found in geological 

 formations older than the Pliocene or latest of the Tertiary strata 

 have yet been detected in any exploring expedition. The lale 

 Prof. Agassiz and Sir Wyville Thom-onwere disappointed in 

 their enthusiastic expectation of finding Ammonites, Belemnite-, 

 and other Old-World foNsils in a living state. I have dredged 

 Miocene fossils on the coasts of Guernsey and Portugal, the 

 latter at considerable depths ; but they were petrifactions and 

 must have come from some fcssiliferous formation in the adjacent 

 land, or perhaps in the sea-bed. 



* " Notes of a Naturalist on the Challcnser," 



Sir Wyville Thomson, in his " Report of the Scientific Results 

 of the Voyage of H.MS. Challenger," ha.^ expressed his opinion 

 as to the doctrine of evolution, that "in this, as in all cases in 

 which it has been possible to bring the question, however 

 remotely, to the tet of observation, the character of the abyssal 

 fauna refuses to give the least support to the theory w hich refers 

 the evolution 'of species to extreme variation guided only by 

 natural selection." I cannot understand how either " natural 

 selection" or "sexual selection" can affect marine invertebrate 

 animals, w hich have no occasion to struggle for their existence 

 and have no distinction of sex. 



( To be continued. ) 



THE RELATION BETWEEN ELECTRICITY 



AND LIGHTS 

 "pVER since the subject on which I have the honour to speak 

 to you to-night was arranged, I have been astonished at my 

 own audacity in proposing to deal in the course of sixty minute^: 

 with a subject so gigantic and so profound that a course of sixty 

 lectures woud be quite inadequate for its thorough and exhaustive 

 treatment. 



I must indeed confine myself carefully to some few of the 

 typical and most salient points in the relation between electricity 

 and light, and I must economise time by plunging at once into 

 the middle of the matter without further preliminaries. 



Now when a person is setting off to discuss the relation between 

 electricity and light it is very natural and very proper to pull him 

 up short with the two questions ; What do you mean by electricity ? 

 and What do you mean by light? These two questions I intend 

 to try briefly to answer. And here let me observe that in 

 answering these fundamental questions I do not necessarily assume 

 a fundamental ignorance on your part of these two agents, but 

 rather the contrary ; and must beg you to remember that if I 

 repeat well-known and simple experiments before you, it is for 

 the purpose of directing attention to their real meaning and 

 significance, not to their obvious and superficial characteristics : 

 in the same way that I might repeat the exceedingly familiar 

 experiment of dropping a stone to the earth if w'e were going to 

 define what we meant by gravitation. 



Now then we will ask first, What is Electricity? and the simple 

 answer must be. We don't know. Well, but this need not 

 necessarily be depressing. If the same question were asked 

 about Matter, or about Energy, we should have likewise to reply. 

 No one knows. 



But then the term Matter is a very general one, and so'is the 

 term Energy. They are heads, in fact, under which we classify 

 more special phenomena. 



Thus if we were asked what is sulphur, or what is selenium, we 

 should at least be able to reply, A form of matter ; and then 

 proceed to describe its properties, i.e. how it affected our bodies 

 and other bodies. 



Again, to the question. What is heat ? we can reply, A form of 

 energy ; and proceed to describe the peculiarities which dis- 

 tinguish it from other forms of energy. 



But to the question. What is electricity ? we have no answer 

 pat like this. We cannot assert that it is a form of matter, 

 neither can we deny it ; on the other hand, we certainly cannot 

 assert that it is a form of energy, and I should be disposed to 

 deny it. It may be that ele;tricity is an entity per se, just as 

 matter is an entity fer le. 



Nevertheless I can tell you what I mean by electricity by 

 apt ealing to its known beliaviour. 



Here is a battery, that is, an electricity pump : 'it will drive 

 electricity along. Prof. Ayrton is going, I am afraid, to tell you, 

 on the 20th of January ne\t, that it produces electricity ; but if 

 he does, I hope you will remember that that is exactly what 

 neither it nor anything else can do. It is as impossible to 

 generate electricity in the sense I am trying to give the word, as 

 it is to produce matter. Of course I need hardly say that Prof. 

 Ayrton knows this perfectly well ; it is merely a question of words, 

 i.e. of what you understand by the word electricity. 



I want you then to regard this battery and all electrical 

 machines and batteries as kinds of electricity pumps, which drive 

 the electricity along through the wire very much as a water-pump 

 can drive water along pipes. ^Vhile this is going on the wire 

 manifests a whole series of properties, which are called the 

 properties of the current. 



■ A lecture by Dr. O. J. Lodge, delivered at the London Institution o 



