March 31, 1881J 



NA TURE 



507 



galvanometer should show a stronger current of electricity pass- 

 ing, on the principle that most, if not all, non-metallic tub- 

 stances that are conductors of electricity become better conduc- 

 tors on the appHcation of heat. I judge that the galvanometer 

 test would be a very perfect one. GEORGE B. Richmond 



Lansing, Michigan, U.S.A., March 5 



The Oldest Fossil Insects 



I SHALL be glad if you will afford me an opportunity of 

 explaining one or two personal matters referred to in p. 11 of 

 Mr. Scudder's memoir on the Devonian Insects of New Bruns- 

 wick, which was mentioned in your last number (pp. 483, 4). 

 He very justly takes exception to some bibliographical and 

 orthographical errors committed by me in Traits. Entom. Soc. 

 Lond. 187 1, pp. 38-40, in a notice of fossil insects named and 

 described by him, and naturally regards them as evidence of 

 insufficient study of the literature relating to them. It is difficult 

 to say preci>ely what happened upwards of ten years ago, but I 

 am satisfied that the mistakes niut have arisen in one or the 

 other of these two ways. Either I attributed the authorship of 

 the names to the person v\ ho first published figures of the fossils, 

 on the ground that names bestowed upon insect-fossils by the 

 publication of description^, without accompanying figures, rank 

 as mere "Catalogue" or MS. names devoid of priority ; or else 

 they are due to circumstances under which the citations were 

 collated. Closely pressed for time, and without much experience 

 in the .art of citation, it is as likely as not that, after forming an 

 opinion upon the plates and consulting the letterpress to see what 

 the author had to say about them, I referred from force of habit 

 to the title-page of the volume for the date of publication and 

 the author's name, instead of turning to the heading of the article 

 for this last. 



In the same page of his memoir Mr. Scudder alludes to the 

 following passages in p. 39 of my work, over which we had 

 some fun when he was last in England, though the strictures 

 were not aimed at him more than at the others. "Paleon- 

 tologists have adopted a ridiculous course with regard to some 

 insect fus^-ils. Whenever an obscure fragment of a wellreticu- 

 late insect's wing is found in a rock, a genus is str.iightway set 

 up, and the fossil named as a new species. The species is then 

 referred to the Ephemeriduc, and is immediately pronounced to 

 be a synthetic type of insects at present distantly related to one 

 another in organisation. This enunciation of synthetic types is 

 often nothing less than a resort to random conjecture respecting 

 the affinities of animals which the writer is at a loss to classify. 

 An insect allied to the EphetiteruUi which chirped like a locust 

 (such as Xciwneura is imagined to have been), is a tolerable 

 sample of these synthetic types. When a fossil comprises only 

 a fragment, or even a complete wing of an Ephemerid, it is 

 hardly possible to determine the genus, and impossible to assert 

 the species. Tlie utmost that can be learned from such a speci- 

 men is the approximate relations of the insect. Ncuration by 

 itself is not sufficient to define the species or even the genera of 

 recent Ep/icmertdce." What I meant to be deduced from this 

 was tha', where in the nature of things actual precision is un- 

 attainable, palceontologists should be content to learn and state 

 the "approximate relations" of fossil insects, and not presume 

 upon the ignorance of scientific men in the matter of genera and 

 species. And I further thought that the Ep/ie/neriJ,e had served 

 quite long enough as an asylum for fossil cripples; I wished to 

 intimate gently that refuse of other groups of insects should 

 be henceforth "shot" elsewhere. 



Mr. Scudder does not know by whom the Devonian insects 

 "have all been regarded as allies of the E]'hemerid:e." My 

 authority for stating such to have been the case is Sir John Lub- 

 bock's Presidential Address in Trans. Ent. Soc London, v. ; 

 Troc. cxxviii. (1S68), where " llaplophlebium Barnesii ... is 

 referred to the Ephtmerina," and likewise " P/atep/iemera 

 antiqua, Ilomothetus fossilis, Lithentomon Hartii, and Xenoneura 

 antiquoruin" are said to be "all Neuroptercus and allied to the 

 Ephemeridse." As members of this family they are quoted liy 

 Marschall. Dyscriitis vcttisius vi3sn>:>i cited by Sir John; but 

 since Mr. Scudder now states it (p. 22) to be "most closely 

 allied " to Horaothetus, there was no harm doLe in classing it 

 with the rest. 



The reason why I thought, prior to the publication of Dr. 

 Hagen's letter in Nature, that Platephemera might have been 

 an Ephemeron, was that in some respects Mr. Scudder's figure 

 presents an appreciable likeness to the neuration of the fore- wing 



in species of Palingenia, of which I possess unpublished 

 drawings ; but these certainly are not quite so odonatous in 

 detail as Platephemera. Without inspecting actual specimens-, 

 it is hazardous to pronounce an opinion about fossils. 



A. E. Eaton 

 Chepstow Road, Croydon, S.W., March 28 



Oceanic Phenomenon 



From the description given by Dr. Coppinger of the "con- 

 fervoid alga" observed on board II.M.S .4!ert some 200 miles 

 to the southward of Tongatabu (Nature, vol. xxiii. p. 482), the 

 conferva in question would appear to be of a species similar to 

 that from which the Red Sea is said to obtain its name. Whilst 

 proceeding up the Red Sea in H.M.S. Hornet during the month 

 of June of last year, I had many opportunities of observing 

 the dirty-reddish scum on its surface — a phenomenon which must 

 be familiar to all navigators of this sea. Each of the little 

 bundles composing it measured about 7,'^th of an inch in length and 

 jj^th in breadth, and contained from twenty to fifty filaments, 

 each filament being composed of a Inear series of short cells, 

 and measuring ^jtsit'Ii of ^n in<^'i '" breadth. I did not observe 

 the discoid bodies referred to by Dr. Coppinger, but their absence 

 may be explained by assigning to this conferva a particular 

 season for the protiuclion of these bodies. Scattered among the 

 bundles were tiny spherical bodies possessing a bristly appear- 

 ance, which proved to be formed of a confused network of the 

 filaments that composed the bundles. 



This conferva would appear to have a very wide distribution. 

 It was observed by Mr. Darwin near the Abrothos Islets which 

 lie off the east coast of South America ; and it is with regard to 

 this phenomenon that the author of the "journal of the Beagle" 

 thus writes : — " Mr. Berkeley informs me that they are the 

 same species (7>2V/;tfi/c'Jw««w eryt/irie!ii>t)vi\\h. that found over 

 large spaces in the Red Sea, and whence its name of Red Sea 

 is derived. In almost every long voyage some account is given 

 of these conferva:. They appear especially common in the sea 

 near Australia ; and off Cape Leeuwin I found an allied but 

 smaller and apparently different species. Capt. Cook in his 

 third voyage remarks that the sailors gave to this appearance the 

 name of sea sawdust." H. B. GUPPY 



17, Woodlane, Falmouth, March 28 



The Banks of the Yang-tse at Hankow 

 At the end of January, 1878, when the w aters of the Yang-tse 

 occupied their lowest level, I had the opportunity of examining 

 the left bank of the river immediately below the foreign settle- 

 ment. The bank, which varied from thirty to thirty-five feet in 

 height, did not present a single perpendicular face, but was cut 

 up into two or more terraces formed by the lingering of the 

 waters at those levels for some extent of time. A calcareous 

 It am, homogeneous in appearance and dark in colour, composed 

 the entire bank with the exception of the upper portion, where 

 a layer of sand a few inches in thickness separated two layers of 

 laminated loam, each of them of similar thickness. After a 

 little trouble I was enabled to observe that the apparently homo- 

 geneous loam was made up of fine horizontal layers varying from 

 one-thirtieth to one-tenth of an inch in thickness ; but the lamin- 

 ation W.1S often concealed ; and it was only where the ham had 

 been freshly broken away that the layers were sufficiently distinct 

 to be coanted. Shells were embedded in the loam, but mostly 

 in the lower half of the bank ; those of the genus " Paludina " 

 were the most abundant, whilst bivalves of the genus " Cor- 

 bicula" occurred, but not in any numbers. The upper three 

 feet of the river-bank were riddled with the burrows of annelids, 

 and these burrows were often filled with little rounded masses of 

 loam, evidently the excrementiti','Us droppings of the worms. 



If, as in the case of the alluvial valley of the Nile, it be con- 

 sidered that each of the fine layers which compose the bank of 

 the Yang-tse was deposited during the periodic annual inunda- 

 tion of the river, then eveiy layer will represent a year's deposit; 

 and taking the average thickness of each layer to le one-twentieth 

 of an inch, it would require twenty years to form an inch and a 

 century to form five inches ; w hilst the whole thickness as ex- 

 posed in the river-bank would require for its formation a period 

 of between 7000 and 80CO years.' 



^ The borings and excavations round the pedestal of the statue of Kameses 

 at Memphis enabled Mr. Horner to estimate the rate of deposition of the 

 alluv.um of the Nile at 3^ inches in a century. (Vide Lyell's "Principles 

 of Geokgy.") 



