52 



NA TURE 



{Nov. 19, 1885 



we are not surprised to find that Jelletf's work is difficult 

 of access to general readers, and on this ground, if on no 

 other, we welcome the present attempt to Ijring the 

 "Calculus" to the fore again. The author follows Airy 

 and Todhunter in the view he takes of a variation, and 

 Jellett and Strauch in the treatment of varying functions, 

 but he has not neglected to give fairly full accounts of 

 the conceptions and methods of other writers. 



A good deal of the preface is taken up with details 

 which might well be omitted should the work reach a 

 second edition, as we hope it may. 



There are in all five chapters (568 and xvii. pages) 

 printed in good type and in e.xcellent style. 



Chapter i., maxima and minima of single integrals, 

 involving one dependent variable is broken up into ten 

 sections : Chapterii., maxima and minima of single integrals 

 involving two or more dependent variables in two sec- 

 tions : Chapter iii., maxima and minima of multiple 

 integrals in six sections. Chapter iv., applications to 

 determming the conditions which will render a function 

 integral one or more times in two sections. 



Chapter v. gives a historical sketch of the rise and 

 progress of the calculus of variations founded upon Tod- 

 hunter's "History," and closes with an account of the 

 " Researches in the Calculus of Variations," referred to 

 above. 



We have nothing to say of Mr. Merriman's work in 

 addition to what we have said already (N.^ture, vol. 

 XXX. p. 334) ; the works are identical, except in the title 

 pages. 



LETTERS TO THE EDITOR 



[T/ieEditordoes not hold himself responsible/or opinions expressed 

 by his correspondents. Neither can he undertake to return^ 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containinginterestingand novel facts.'\ 



Italian Aid to Biological Research 



The Committee appointed by the Royal Academy of the 

 Lincei in Rome at the request of H.E, the Minister of Naval 

 Affairs, to see that the best possible use in the interests of 

 science be made of the natural history specimens collected by 

 officers of the Royal Italian Navy, wishes to make known to 

 all students of biology that rich material for study, consisting 

 of a certain number of plants and extensive collections of ani- 

 mals of nearly all classes, is at present deposited at the Zoologi- 

 cal Station at Naples. This material has all been collected by 

 the officers of the Royal Navy, principally by the Viltor Pisani 

 in a recent voyage round the world, and by other Italian men- 

 of-war in the Red Sea and the .<^gean Sea. These collections 

 have been preserved by the best and most modern methods, and 

 can be used for histological and morphological researches, in 

 accordance with the actual requirements of science, as well as for 

 systematic and faunistic investigations. The Committee places 

 this rich material at the disposal of the men of science of all 

 countries who will ask to take part in its illustration, either to 

 complete monographs in course, or for monographical works or 

 for special research on any organic system of a given group. 



The requests, on which the Committee will decide, are to be 

 seHt to Prof Trinchese, University of Naples. 



Prof Tri.nchese, Naples 



Prof Todaro, Rome 



Prof Passerini, Parma 



Prof. GlGLIOLI, Florence 



Lieutenant Chierchia (Royal Italian Navy), 

 Naples 



Prof. DoHRN, Naples 



The Resting Position of Oysters 



In a letter from Mr. J. T. Cunningham in your impression of 

 Nature of October 22 (p. 597) it is sought to show that the 

 oyster does not rest on its left but on its right valve. The 

 evidence which appears to him conclusive on this question is 

 " that the right fiat valve is always quite clean, while the convex 

 valve is covered with worm-tubes (Stylea grossularia) and 

 Hydroids. " 



This observation is correct on the whole, but not decisive for 

 the question under consideration. After reading Mr. Cunning- 

 ham's letter I proceeded to examine 140 oysters in my collection 

 of Schleswig oysters, and found only on a few right valves a 

 worm (Pomatociros tricuspis) or a Cirripede [Balanus crenatus), 

 whereas on many left valves I distinguished sponges (Halt- 

 chondria panicta), Alcyoniurn digitatum, Hydroids {Strtztlaria 

 argentca, Tubularia indivisa, Eadendrium rameum), Bryozoa 

 (.4U-yonidiu7H gelatinosum), Balanus crenatus, Pomatoceros tri- 

 cuspis, or Sabellaria anglica. Of the 140 oysters examined 43 

 still bore on their shells the body on which as spawn they had 

 reared themselves, namely pieces of oyster-shells, Mylilus edulis, 

 Alya arenaria, Mya truncata, Cardium edule, or Buccinum 

 undatum. All these adherent bodies were attached to the 

 nucleus of the left valve, not one single piece to the nucleus of 

 the right. And this is a circumstance decisive in the question 

 raised by Mr. Cunningham. The places on the right valve, 

 where living animals rest, did not stick close to fixed bodies, 

 but the water flowed freely over them, thus admitting embryos 

 to settle on them. The bottom of oyster banks is not a smooth 

 surface, but is formed mainly of old oyster-shells on which many 

 living oysters do not assuredly plant themselves closely and hori- 

 zontally, but lie often obliquely. It is thus that Hydroids, Sponges, 

 Alcyonium, and Alcyonidium, having settled on the right lower 

 valve, are enabled to grow freely in the water and without let or 

 hindrance develop to the length of four or five inches. 



Kiel, October 31 Karl MoBrus 



Universal Secular Weather Periods 



I DO not want to pose as a statistical cycle-hunter, or to bolster 

 up any mere apparent local periodicity of a certain meteoro- 

 logical element, but I wish to place before your readers the ap- 

 pended independent paragraphs from two journals, one on each 

 side of the Atlantic, and to ask any unprejudiced person if we 

 have not here some preliminary evidence (all the more valuable 

 from its being so evidently incidental and unconscious) in favour 

 of the march of certain secular weather areas, possibly connected 

 with barometric waves, similar to those traced out by Messrs. 

 Chambers and Pearson in India, across the Atlantic, from 

 America to Europe. 



I would not submit such slt;nder evidence to criticism were it 

 not that it concurs entirely with certain views put forward by 

 myself in a recent paper in the Royal Meteorological Society's 

 Quarterly J ou> nal , on "The Height of the Neutral Plane of 

 Pressure in India," and that I have long felt that the entire 

 question demands attention both on scientific and economical 

 grounds. Also both paragraphs include last year, thus bringing 

 the apparent periodicity up to date. 



Being at present fully engaged in two other branches of re- 

 search, I am unable just now to take up this hopeful and important 

 problem, but I would suggest that if we ever intend to forecast 

 the general character of the weather of a season or year, which 

 even in this country undergoes long periodic changes, during 

 which it remains for weeks and months together of the same 

 type, some such method as the following must be adopted : — 



Annual and seasonal mean barometric charts must be con- 

 structed from records at principal stations in America, Europe, 

 and Asia for the past fifty or sixty years, and from them baro- 

 metric abnormals for each year, and for each season, must be 

 calculated, and charted. An examination of these ought to 

 throw great light on, if not to some extent solve, the question of 

 the motion of the larger pressure areas which in turn guide and 

 control the motion of the smaller diurnal systems. The work 

 would, I admit, be one of some considerable magnitude, but 

 surely it is one imperatively demanded in the interests of 

 the science, besides being a priori likely to yield valuable 

 results. It has long been a cherished idea of mine to endeavour 

 to carry out the scheme myself, and it is only because I feel pre- 

 cluded from doing so at present by the pressure of other work 

 that I throw out the suggestion for the benefit of any who feel 

 disposed to take it up. 



