May 1 6, 1872] 



NATURE 



45 



land was but small in proportion, and after swaying about for a 

 few yards, died away. 



I have been informed of similar cases in this district, but the 

 above is the only instance in which I observed a waterspout 

 myself. Sydney B. J. .SkiiRTchi.y 



II.M. Geological Survey, Wisbech, May 2. 



The Geologists' Association at Watford 

 In the notice in your last number of the excursion of the 

 Geologists' Association to Watford there is a slight error which 

 perhaps I may be permitted to correct. 



The sections of the Woolwich and Reading Series which were 

 examined are at Watford Heath Kiln :;nd at ISushey Kiln (not 

 liiishey Heath), and the formation, although varying very much 

 in the sliort distance (scarcely a mile) that these places are apart, 

 is at each place represented by beds of clay, sand, and pebbles. 

 Tlie pebble beds are, however, better seen at tlie latter tlian at 

 the former place. John HonciNSON 



Temperature of Hill and Valley 



In Nature of .May 2, page 19, there is an interesting report 

 of a paper by Mr. Dines " On the Temperature of Hill and 

 Valley," showing that (to use Mr. Gaiter's words in the discus- 

 sion) " the air is colder on the top of the hill than in the valley, 

 by d.ay, when the sun is shining, and warmer at night when it is 

 not shining." This appears anomalous at first sight, but I 

 believe it has long be<n known, and it is easily exp'ained. The 

 temperature of the hill top is not produced where it is observed. 

 As Mr. Glaisher sta*ed in tlie same discussion, the higher we go 

 in a ba'loon the less is the range of temperature ; and the tem- 

 perature at the top of a liill whicli is at all isolated, or even steep 

 on one side, approximates to that observed in a balloon at the 

 same absolute height. 



The reason why temperature has a less range in the higher 

 atmospheric strata, is that the earth has very much more power of 

 both absoibing and radiating heat than the molecules of air, and 

 consequently heats more rapidly in the daytime and cools more 

 rapidly at night. The temperature of air at the surface of the 

 earth is determined much more by the absorption and radiation 

 of the earth than by its own. 



The truth of this view U shown by the fact that the law is 

 quite different for table-lands from that which we have seen to 

 be true for isolated hills. On table-lands the diurnal range of 

 temperature is greater than on low plains, though on isolated 

 hills it is less. These facts appear to show that while, other 

 conditions being given, the mean temperature of a station chiefly 

 depends on its height above the sea level (or, in other words, 

 the thickness of the atmosphere above it) the diurnal range at 

 the station (whether hill top or balloon) chiefly depends on the 

 proximity of the atmospheric stratum surrounding it to the 

 surface of the earth. 



The fact stated in the same paper that "in cold weather the 

 air on the top of the hill is never so cold as that in the valley," 

 is no doubt partly due to the cause above stated, but partly also, 

 I think, to the fact that cold air is heavier than watm, and seeks 

 the loweft position. I believe there is no doubt this is the ex- 

 planation of the g/i!iih:!s or freezing caverns of the Jura described 

 in the Rev. Harold Browne's book. 



Joseph John Mukphy 



Old Forge, Dunmurry, Co. Antrim, May 8 



Meteors 



I OBSERVED a meteor at about half-past eleven on the night 

 of the 8th inst., in the cons'ellation Scorpio, which passed very 

 close to the star Antares, travelling from right to left. 



It appears to me worth rem-.rking from the fact of its course 

 lying very near, and roughly parallel to, that p.art of the ecliptic 

 which corresponded to the earth's position in her orbit. 



It traversed some eight or ten degrees of arc, and was visible 

 for three or four seconds, gradually increasing in brightness till 

 it was nearly on a par with Antares, which star it also resembled 

 in colour. Its slow apparent motion immediately suggested the 

 idea that it was moving in the same plane and direction as the 

 earth ; in fact, that it was overtaking us in an orbit just outside 

 our own. 



The course of another meteor, seen about half an hour earlier 

 from a westerly window, and described to me as not very inferior 

 to Jupiter, appears also to have lain in the direction of the 



ecliptic, but from left to right, in the neighbourhood of the con- 

 stellations Gemini, Cancer, or Leo. 



It is rash to generalise from such insufficient data, but I con- 

 ceive these meteors may both have belonged to a system whcse 

 orbit lies nearly in the plane of the earth's ; the apparent retro- 

 grade motion of the last-named being caused by the direction of 

 its path crossing our orbit at a point behind the earth's then 

 place instead of in advance of it, 



Cardiff, May 10 Geo. C. Thompson 



The Ivory Crayfish 



I THINK it may be interesting to some of the readers of Nature 

 to know that a specimen of the "Ivory crayfish," or Astiuiis 

 ( Caiiiliarus) prllucidus, mentioned in the very interesting commu- 

 nication of Dr. Packard on the Mammoth Cave of Kentucky in 

 NATUitE, April 18, has been living in the aquarium-house in the 

 Regent's Park for a considerable time. The specimen was brought 

 over at the close of the last year by Mr. Boyd from the Mammoth 

 Cave ; it is row placed in the first frcsh-watcr tank on the right 

 hand of the visitor as he enters the aquarium. Its daik-loving 

 habits do not permit it to be seen much, as it generally burrows 

 parti.illy under a large stone, from beneath which only the tips 

 of its white claws can be seen. 



Culverlea, Winchester, May 8 W. A. Forbes 



THE AMERICAN ACADEMY OF SCIENCES 

 'T^HE Annual Meeting of the National Academy of 



-•■ Sciences was convened, on the i6th of April last, at 

 the .Smithsonian Institution in Washington. The exist- 

 ence of this body was authorised by an Act of Congress 

 passed in 1863 ; and it was originally limited to fifty 

 members, designed to represent the most eminent men of 

 science in the country, who were to be organised for the 

 purpose of serving as advisers to the United States 

 Government in questions of a scientific nature. The 

 Academy has rendered excellent service in this capacity, 

 and has had referred to it very many impoitant questions, 

 the satisfactory solutions of which have saved much money 

 to the Government, and increased the efficiency of many 

 of its bureaus. One condition of membership is that all 

 such service to the Government is to be performed with- 

 out charge. 



As this Society, by its national character, takes the lead 

 of State Institutions for a similar object, and the number 

 of members was at first limited, considerable dissatis- 

 faction was felt by many persons who believed themselves 

 worthy of membership, but were e.xcluded by this restric- 

 tion. The Academy, therefore, after mature deliberation, 

 decided to ask Congress to remove the limitation as to 

 number, which being done, the principal business of the 

 Academy at its late meeting consisted in the increase of 

 its force. Twenty- five new members were selected, repre- 

 senting the various branches of theoretical and applied 

 science, and the number is to be increased by five each 

 succeeding year. Very few papers or communications 

 were presented to the Academy, as all the time of the 

 meeting was required in carrying out the changes involved 

 by the alteration of the charter, including the formation 

 of a new constitution and rules for its government. 



The following is the list of members elected : — Prof. C. 

 A. Young, Dartmouth ; Prof. E. D. Cope, Philadelphia ; 

 Prof. J. Lawrence Smith, Louisville ; W. S. Siilli\ant, 

 Colcmbus ; Prof. W. B. Rogers, Boston ; J. H. Trumlu]l 

 Hartford: Prof. J. P. Cooke, Cambridge; Dr. A. S 

 Packard, jun., Salem ; Prof. W. P. Trowbridge, New 

 Haven; J. E. Oliver, Massachusetts ; Prof E. W. Hilgard, 

 Oxford, Maine ; Prof. R. Pumpelly, State Geologist, Mis- 

 souri ; Prof. J. H. Lane, Coast Survey ; Prof. A. E. Vcr- 

 rill. New Haven ; Dr. J. W. Crafts ; Theodore Lyman, 

 Boston : Prof. A. M. Mayer, Stevens Institute, Hcbokcn ; 

 Prof. H. J. Clarke, Amherst ; J. Ericsson ; Prof. Hadlty, 

 New Haven ; Dr. F. A. Genth, Philadelphia; Charles A. 

 Schott, Coast Survey i Prof. A. H. Worthen, State Geolo 

 gist, Illinois ; Captiya J. B. Eads, St. Louis ; General H. 

 L. Abbott, U.S.A. 



