572 



NA TURE 



{Oct. 26, 1S76 



present instance we desire to draw their attention to an 

 important paper by Prof, Flower, F.R.S. {Proc. Zoolog. 

 Soc. 1876, p. 443), just published, on the differences be- 

 tween the skulls of the same two species. There are 

 thirty skulls of single-horned rhinoceroses in the two 

 great metropolitan zoological museums, and from a com- 

 parison of these Mr. Flower has been able to draw 

 several important conclusions. One of these is that in the 

 Indian Rhinoceros (/?. unicornis) the posterior termina- 

 tion of the bony nostrils (the mesopterygoid fossa) is con- 

 siderably narrower than in the Javan species {R. son- 

 daicus),\x. the same time that the vomer terminates 

 behind by becoming lost, through fusion, in the pterygoid 

 processes, instead of ending free, lamelliform, and pointed. 

 In the Indian rhinoceros, also, the upper grinding teeth 

 have a pattern which is easily distinguishable from that 

 of the Javan animal, a peculiar little circular " accessory 

 valley " being developed in the first and second molars of 

 the former, not found in the latter. In the same paper 

 Mr. Flower also brings forward an interesting difiference 

 between the skulls of the single and double-horned 

 rhinoceroses, the external auditory meatus being embraced 

 below by the fusion of the post-glenoid and post-temporal 

 processes of the squamosal portion of the temporal bone 

 in the one group, whilst in the other these two processes 

 remain separate, as in the horse and tapir. The African 

 species agree with the two-horned Asiatic in this respect, 

 so that the character separates the unicorn from the 

 bicorn Rhinoceroses. 



Passerine Birds. — Within a few pages of the paper 

 above referred to is one by Mr. A. H. Garrod upon some 

 of the peculiarities in the anatomy of Passerine Birds. The 

 nature of the voice-organ is the point laid most stress 

 upon. For a long time it has been known that there is a 

 small section of the Passerine birds which has no mus- 

 cular organ of voice that may be employed for singing. 

 These all were supposed to inhabit America, although 

 from the conformation of their wings, wherein they alone 

 resemble the aberrant genera just mentioned, Herr 

 Cabanis, of Berlin, as long ago as 1846, predicted that 

 the Old World Ant Thrushes {Pittidce), lacked the voice 

 organ. Mr. Garrod, from a dissection of several speci- 

 mens of two species of Pitta, demonstrates that Cabanis 

 was quite correct in his surmise, and that the voice-organ 

 is absent in them. He also describes the same organ in 

 the Lyre Bird of Australia {Menura superbd), and in its 

 diminutive and interesting ally Atrichia riifescens. The 

 paper ends with an outline plan of the classification which 

 introduces more than one novel feature. 



BAROMETRIC VARIATIONS 



T N the " Notes," Nature, vol. xiv. p. 464, 1 see reference 

 ■^ is made to my results on this subject, and it is 

 suggested that General Myer's International observations 

 will be of the greatest value in connection with the ques- 

 tion whether there may not be some other attractive force 

 than gravitation connected with these variations. 



I had come to the conclusion nearly twenty years ago 

 (see British Association Transactions for 1859) that the 

 mean pressure of the atmosphere for the whole globe was 

 probably less for July than for January. This conclusion 

 was derived from observations made at a great number 

 of stations in both hemispheres during these months in 

 the same year (1844). A considerable part of the earth's 

 surface was not covered by these stations. About a year 

 ago I received from Gen. Myer a copy of the Bulletin 

 oj International Obsejvations made on February 7, 

 1S75, at 7h. 35m. A.M., Washington Mean Time, and I was 

 glad to see in such observations the means of makmg 

 more complete comparisons of the mean barometric 

 pressure for given instants on different days. It was only 

 a few months later that I found I could obtain a sight of 

 ether Bulletins at the Meteorological Office. I had time, 



however, to compare only two Bulletins, that sent me by 

 Gen. Myer for February 7, and another for the 27th of 

 the same month (1875) which seemed to show a lower 

 pressure generally than the first. Other investigations 

 have prevented me from seeking for a larger series of 

 Bulletins to carry out the comparisons ; but it seems to 

 me that the comparison then made is sufficiently inter- 

 esting to mei-it notice. 



The mean barometric pressure at 7h. 35m. A.M., Wash- 

 ington M.T., was found for each of the countries in the 

 Bulletifi, on each of the two days mentioned ; the differ- 

 ences of these mean pressures were then taken ; they 

 are given, with the numbers of stations from which the 

 results are obtained, in the following table : — 



Kr..™i,„ „<• Difference of 



Country. ^cVl^^fl"^ Pressures. 



Russian Empire 



Denmark 



Greenland, Iceland, and Faroe 



Norway 



Austria 4 



Turkey 



Number of 

 Stations. 



.. 23 ... 



.. 3 ••• 



.. 3 ... 



.. 3 ••• 



.. 12 ... 



S ■■■ 



-f 0-19 



-f 0-2I 

 - 048 

 + 033 



■¥ 006 

 + 0-19 

 + 015 

 + 0-30 



■V 0-68 

 + 0-32 

 -f 0-27 

 -1-052 

 + 0-55 

 + 0-54 

 + 0-27 

 + 0*26 

 + 032 

 + 0-53 

 + 0-37 

 + 009 

 + o 21 



O'OO 



Mediterranean, Gibraltar, Corsica... 3 .. 



Germany 21 



Switzerland 2 .. 



Italy .. 13 .. 



Algeria 9 .. 



Netherlands 4 .. 



Belgium i 



France 21 



Spain I .. 



Portugal I .. 



Great Britain and Ireland 41 .. 



Canada ... 18 .. 



United States 96 .. 



West Indies 7 .. 



Ceylon i 



Cape of Good Hope and Natal ... 2 



It will be seen that, with the exception of the small 

 area about Iceland, all the differences are positive ; 

 or the barometer stood higher on February 7, 1875, at 

 7h, 35m. A.M. W. M.T., than on the 27th at the same 

 hour. I have no doubt that when the investigation is 

 made with the care it merits, much more marked re- 

 sults will be obtained. All these series, however, with 

 the exception of the last two stations, are in the northern 

 hemisphere ; it is then of course possible that the atmo- 

 sphere was playing at " hide and seek " with us, and had 

 moved away to places for which no observations are at 

 present forthcoming. There may also have been some 

 difference in the amount of vapour in the air on these 

 two days ; this I have not attempted to calculate, but for 

 two days in February, in the northern hemisphere, it will 

 probably be very small. ^ 



In the first investigation already referred to, I had 

 calculated the mean tension of vapour in the lowest 

 stratum of the atmosphere for each station ; this, it is 

 now agreed, does not indicate the pressure of vapour on 

 the barometer, but the result was that the vapour tension 

 was greatest in July, when the mean barometric pressure 

 was least. A reason for the increased mean vapour ten- 

 sion for the whole globe in July will be found in Dove's 

 result that the mean temperature of the whole atmosphere 

 is greatest in that month. I shall probably take the 

 liberty of returning to this subject. 



John Allan Broun 



I I see from the Bulletin in my possession (that for February 7) that the 

 thermometer was, on the average, below zero (centigrade) m Europe, and 

 from 10° to 30° below zero in America ; the higher pressure on the 7th 

 could scarcely then be due to the vapour in the air. For any considerable 

 exactness in such comparisons, series of observations like those of General 

 Myer should contain the obseT-ztcd pressures lor each station (or the correc- 

 tion to the sea- level) as well as the calculated . ea-level pressures ; since if, at 

 any high level station, the observed pressures are e-xactly the same on two 

 days one of which has a higher temperature than the other, the calculated 

 pressures for the sea-level will differ, that for the lower tempeiature being 

 highest. _ The greatest mean error due to this cause in the present instance 

 will not, in all probability, exxeed -boot inch. 



