July 15, 1897] 



NATURE 



253 



the bottles recovered, eighty-one were thrown overboard in the 

 North Atlantic, and these are the only ones dealt with upon 

 the chart in question. Taken collectively, the courses followed 

 by the bottles elucidate the main principles of oceanic circu- 

 lation, and show the close agreement that exists between the 

 motion of the surface water and the direction of the prevailing 

 winds. Dividing the list into groups, according to latitude, 

 and dealing only with those bottles whose drifts exceed 

 300 miles, we have the following average velocities of the daily 

 drift : — North of 50^, 5 '3 miles ; between 40° and 50°, 5 "3 miles ; 

 between 20" and 40°, 5 miles ; between 0° and 20°, 9*8 miles. 

 A noteworthy drift shown on the chart, is that of a bottle thrown 

 overboard in lat. 2^9' S., long. 30^25'W., and picked upon the 

 African coast, at the mouth of the Bathurst River. This bottle, 

 set adrift in the strong south equatorial current, must have been 

 transferred to the Guinea current, and carried by it to the 

 exceptionally northern position at which it was recovered. 



The Director of the National Observatory at Athens (M. 

 Eginitis), has made an important contribution to the meteorology 

 of Southern Europe by the publication of a careful discussion of 

 the observations at Athens during the present century, and now 

 continued at the Observatory. Although there are several 

 interruptions in the continuity of the earlier observations, they 

 have been carried on regularly during the last thirty-seven years. 

 The discussion, which extends to 220 large quarto pages, contains 

 an exhaustive account of the climate, each element being 

 separately treated, and, in addition to the instrumental ob- 

 servations, notice is taken of all information obtainable from the 

 most ancient periods. The absolute extremes of temperature 

 vary from io5"3'' to I9'6', giving a range of 857'. Rain falls, 

 on an average, during ninety-eight days in the year, the normal 

 annual amount being 16 inches. Athens enjoys a large amount 

 of sunshine, the values recorded by a Campbell instrument in 

 1894 amounted to 2527 hours ; at Eastbourne in the same year 

 the amount registered by a similar instrument was 1669 hours. 

 In some years the sun shines incessantly from morning till 

 evening, for a month at a time. 



That birds play an important part in relation to agriculture 

 has long been known to ornithologists ; but farmers have a 

 tendency to dwell upon the harm they do, rather than the 

 benefits received. A better feeling is, however, being cultivated 

 by means of the publications of the Society for the Protection of 

 Birds, by County Councils, and by a host of books on birds ; so 

 that the hope may be cherished that agriculturists will soon be 

 able to discriminate between their feathered friends and foes. 

 In the United States, serviceable knowledge of this character is 

 communicated to all who are concerned with it. For instance, 

 in the Fanners' Bulletin (No. 54), which has just been issued 

 by the U.S. Department of Agriculture, Mr. F. E. L. Beal 

 ■describes " Some Common Birds in their Relation to Agricul- 

 ture." The Bulletin contains short accounts of the results of 

 food studies of about thirty grain and insect eating birds belong- 

 ing to the different families. It is pointed out that the value of 

 birds in controlling insect pests should be more generally recog- 

 nised ; for while it may be an easy matter to exterminate 

 the birds in an orchard or cornfield, it is an extremely difficult 

 one to control the insect pests. How very valuable birds are, 

 is illustrated by the fact that during the recent plague of Rocky 

 Mountain locusts in the Western States, it was found that 

 locusts were eaten by nearly every bird in the region, and that 

 they formed almost the entire food of a large majority of this 

 species. In winter sparrows are active weed destroyers, weed 

 seed forming an important item of the winter food of many of 

 these birds. 



The uncertainty which attaches to the specific-heat-ratio of 

 ^ases as a means of distinguishing between monatomicand poly- 

 NO. 1446, VOL. 56] 



atomic molecules renders it of great interest to investigate other 

 properties dependent on the molecular volume or cross-section. 

 In the Proceedings of the American Academy of Arts 

 and Sciences, xxxii. 11, Messrs. A. A, Noyes and H. M. 

 Goodwin describe a new determination of the viscosity of mer- 

 cury vapour and its comparison with those of hydrogen and 

 carbon dioxide, the method used consisting in measuring the 

 flux through a capillary tube under constant difilerence of pres- 

 sure. By the application of O. E. Meyer's formula, the authors 

 deduce that the cross-section of the mercury molecule or of its 

 sphere of action is nearly the same as that of the carbon-dioxide 

 molecule, and about two and a half times as large as that of the 

 hydrogen molecule. Whether the authors are justified in their 

 conclusion, " that atoms and molecules are of the same order of 

 m.agnitude," depends on how far the value of the ratio of the 

 specific heats in mercury is admitted to be indicative, on the 

 kinetic theory, of the monatomic nature of that gas. 



A NOTE has been communicated to the Atti dei Limeihy Dr. 

 Emilio Oddone, on an apparatus for determining the thermal 

 conductivity of substances which are bad conductors. The 

 apparatus is based on the model of one constructed and de- 

 scribed by Dr. Venske, of Gottingen, in 1891, and the author 

 describes a determination made by it for glass. It is proposed 

 to apply the method to the. conductivity of rocks, and we hope 

 that the investigations will throw fresh light on the past history 

 of the earth. 



In a very suggestive, privately published, essay entitled 

 " Demeter und Baubo, Versuch einer Theorie der Entstehung 

 unsres Ackerbaus," E. Hahn puts forward a number of new 

 views, and combats many old ones. He believes that man was 

 primitively an omnivorous ''collector," later he severally 

 diverged into a hunter, a fisher or a planter, or in certain dis- 

 tricts into a herder ; but he denies the evolutionary series of 

 hunter, herder and agriculturist. He argues that the first culti- 

 vated plant was millet, and he draws a sharp distinction 

 between hoe-culture and the cultivation of cereals with the use 

 of the plough. He believes barley was the earliest cereal, and 

 wheat the latest. There is no necessary connection between 

 our method of tillage with the plough (with the keeping of 

 domestic animals), and the use of milk. Cattle were first do- 

 mesticated as draught animals and to draw the plough, and it 

 was only long afterwards that they were trained to yield milk 

 for human food. The author is greatly impressed with the effect 

 of religion on the progress of early culture ; for example, he 

 holds that the waggon was originally employed for the transport 

 of effigies of the goddess of fertility, probably the moon, and that 

 later it became a secular vehicle. He does not believe that 

 wheels were evolved from rollers, but that they were derived 

 from spindle-whorls, four of which were attached to a board, 

 and so arose the diminutive and primitive conveyance of the 

 goddess. The author invites criticism, and would be glad of 

 references to researches bearing on his subject ; these should 

 be addressed to him, care of Max Schmidt, bookseller, Liibeck. 



Herr F. R. Friis has just completed and published the 

 correspondence between Tycho Brahe and Oligerus Rosen- 

 krantz during the years 1596 and 1601. This book, which 

 is entitled " Epistolae quas per annos a 1596 ad 1601 Tycho 

 Brahe et Oligerus Rosenkrantzius inter se dederunt," contains 

 in its 80 pages twenty-four letters, most of which were written 

 by Tycho Brahe to Rosenkranlz. In the appendix are given 

 ten other interesting communications, written about the same 

 time. The compiler of this collection is to be congratulated on 

 the important .service he is rendering history by this collection, 

 which is a further addition to letters already published. The 

 first publication was entitled " Tychonis Brahei et ad eum 

 doctorum virorum Epistolse ab anno 1568 ad annum 1587," and 



