Feb. 19, 1874] 



NATURE 



301 



Washington, of uniform reports mfide from simultaneous obser- 

 vations taken daily at as many of the stations under your charge 

 as it may be practicable for you to instruct or request to furnish 

 such reports, or from other stations from which they may be 

 voluntarily tendered, and of similar reports to be taken at the 

 established stations of this Ofhce throughout the United States. 

 The reports to embrace, at least, pressure (reduced), tempera- 

 ture, wind, rain, relative humidity, and clouds, and to be made 

 at 12.43 r.M., Greenwich mean time. The records to be printed 

 or in manuscript, as you prefer, and lo be mailed (as many of 

 them as may be ready for exchange on tlie dates) in packages, on 

 the 15th and last days of each month. Should circumstances 

 render it inconvenient for your Ofiice to furnish such reports 

 without blanks for days on which they will necessarily fail to be 

 taken, the records wdl be none the less gratefully received. 

 Self-registered records will be very acceptable. In return ex- 

 change it is proposed to mail to your Office on the 15th and 

 last days of each month the record of the simultaneous report 

 prepared for that purpose in the form of which the enclosure 

 herewith is a specimen for a single day. 



" The data so to be exchanged are intended for any use either 

 Office may wish to make of them. 



•'As an acknowledgment to those who may, upon your invi- 

 tation, assist in a work so much wislied for on ^tl^e part of this 

 Office, it is proposed to send to you monthly copies of the 

 'Official Monthly Weather Review,' with its Maps, for distri- 

 bution to each of those so assisting, or other papers published by 

 this Office, if so requested. 



" In requesting this exchange as a part of a system to which 

 it is hoped a very wide extension can be given, the Chief 

 Signal Officer recurs with jileasure to the prompt encourage- 

 ment received at your hands at the earlier steps for its adoption, 

 and is gratified to announce that co-operation for similar ex- 

 changes ot records, commencing on January i, 1874, has been 

 requested or is in progress with Prof. H. Wild, Director, 

 Imperial Observatory, St. Petersburg ; Prof. A. Coumbary, 

 Director, Imperial Observatory, Constantinople, Turkey ; Prof. 

 Carl Jelinek, Director, Imperial Observatory, Vienna, Austria ; 

 Prof Queteltt, Director, Aleteorological Observatory, Brussels, 

 Be'gium ; Prof. Buys Ballot, Director, Meteorological Institute 

 of the Netherlands, Utrecht, Holland ; and Prof. H. Mohn, 

 Director, Meteorologicallnstitiate of Norway, Christiana, Norway. 

 As time and its (acuities will permit, this Office will seek addi- 

 tional aid. The advantages to accrue to the service in the 

 United States are certain, and the hope is not unfounded that as 

 the co-operation sought will be world-wide, so also will be the 

 benefits resulting. — 1 am, &c., 



" Albert J. Myer 



" R. H. Scott, Esq." " Brigadier-General, U.S.A. 



Remuneration of the Contributors to Milne-Edwards' 

 " Mission Scientifique au Mexique" 



En vous remerciant de I'envoi d'un article (vol. i.x. p. 260) 

 rel itif aux singulieres assertions contenus dans une note de M. 

 Gray, je vous demanderai la permission d'ajouter que ni M. 

 Dumeril ni aucun des autres naturalistes qui prennent une part, 

 soit directe, soit indirecte a la publication de I'ouvrage sur la 

 Zmlogiedu Mexique ne recoivent pour ce travail une remuneration 

 pccuniaire quelconque. C'est gratuitement et dans I'interet de la 

 Science seulement qu'ils s'en occupent ; par consequent les ren- 

 seignements foumis a mon estimable ami M. Gray, par je ne sais 

 qui, sont faux. 



Kecevcz, Monsieur, I'assurance de nia consideration tres dis- 

 tingue. Milne-Edwards 



Paris, ce 13 fcvT. Membre de I'lnstitut de France, et 



Associe Etranger de la .Societe 

 Royale de Londres 



Animal Locomotion 



I r is not my intention to go through the detailed proof; of 

 the different statemenis in my review of his work to wliich 

 Dr. Pcttigrewobject.s, and which his letter of last week in no way 

 falsifies, nor to show how he has quite missed the point of an 

 observation of mine which he condemns as ** utter nonsense," but 

 simply to answer the question with which he ends his remarks. 

 At first sight it might seem that the active dilatation of the 



heart during diastole did depend on an inherent power in the 

 muscular fibres of the ventricles to elongate, but the peculiarities 

 of the coronary circulation are quite sufficient to explain the 

 plienomenon without the introduction of so unnecessary a theory 

 as that of Dr. Pettigrew. For in the heart when removed from 

 the body, as in the living body during diastole, the injection of 

 fluid into the coronary vessels causes the whole heart to open up 

 from the congestion of the ventricular walls, and so produce the 

 active dilatation which is well known to occur. This explana- 

 tion was proposed by Bnicke, and by myself some years later 

 (Journal of Anat. and Phys.) 



A. II. Garrod 



While admitting that Dr. Pettigrew appears to have made 

 mistakes in his figures, and that he has not explained his views 

 in the clearest manner, nevertheless it appears to me that, on the 

 very important questicm of whether a bird's wing during onward 

 flight moves downward and forward or downward and back- 

 ward, he is right in asserting the former to be the fact. 



The arguments of Mr. Garrod and Mr. Ward against this view 

 seem to be founded on two .assumptions— that the wing during 

 its down-stroke is an inflexible plane, and that during its up- 

 ward motion the quills open so perfectly that there is neither 

 vertical nor horizontal resistance. But every feather of a wing 

 is highly flexible towards its extremity, so that during the 

 down-stroke the whole posterior margin of the wing must 

 be curved up by the pressure of the air, thus forming a 

 highly effective propelling surface owing to the rapid 

 motion of this part of the wing. During the upward stroke 

 the feathers open freely so as greatly to diminisli, though not 

 wholly to prevent, downward reaction ; but the broad soit web 

 of each quill will be bent down by the rapid escape of air be- 

 tween the quills, and this will necessarily give a forward motion, 

 probably equal to that attained during the down-stroke, in which 

 the small curved surface has a gieater resistance and more 

 rapid motion. If then the up- and the down-stroke both pro- 

 duce onward motion, the resultant of this motion will be in the 

 direction of the mean position of the Avings, which we may take 

 to be about that of the body of the bird ; but if the down-stroke 

 were directed Imck-vard and the up-stroke for~i'ard, the resultant 

 onward motion would lie obliquely downward, and this down- 

 ward angle of motion would tend to be so much increased by the 

 continual gravitation of fe body that the surplus vertical reac- 

 tion of the down-stroke over the up-stroke would not be able to 

 overcome it. A slight upward angle of the mean position of the 

 wing-plane ^e;ms therefore to be essential to secure horizontal 

 forward motion as a general resultant of the upward and do\vn- 

 ward action of the wings under the influence of gravitation ; and 

 to Dr. Pet'igrew belongs the merit of showing that this is one of 

 the most important cliaracteristics of the flight of birds, and, 

 probably in a still greater degree, of that of insects. A bird's 

 wing is a highly complex apparatus, subject to a variety of 

 flexures and motions in every leaiher ; and it is only by a careful 

 consideration of the actioi of t^e resisting medium on these vari- 

 ously curved elastic surfaces, both during theupward and downward 

 motion of the wings, that we can arrive at any definite notion of 

 their supporting and propelling effect. The experiments of 

 Prof. Marey do not seem to contradict the theory of Dr. Petti- 

 grew, as far as 1 can make out from an abstract of these given in 

 the "Ibis" for 1870, p. 267 ; though, as his apparatus only 

 gave the motion ot the wing relatively to the body of the bird, 

 they are not of very much value in determining the absolute 

 angular position of the wings, which is what we want to arrive 

 at. The highly-inclined position of a hovering bird is more to 

 the point, as any less degree of inclination would lead to onward 

 motion. Alfred R. Wallace 



On the Variability of the Node in Organ-pipes 

 The variability of the node is an unrecognised phrase. 

 Something .similar in kind relating to the node will be remem- 

 bered as having been mentioned by scientific writers in a cursory 

 manner, then set aside as evidence of too doubtful interpretation 

 to call for more extended comment. 



I'rom the time of Savart it has been known that the nodal 

 division of the open orgar-pipe does not take place at the exact half 

 of the length, that the half nearest the embouchure is the shorter 

 of these " unequal halves ' — a contradictory term apologised for 

 yet sanctioned, I believe, by the late Prof Donkin. 



The displacement of the node is perhaps the most significant 

 fact that in the natural history of organ-pipes presents itself to 



