January 1, 1886.] 



SCIEXCE. 



13 



ing such surveys possible. It is a step in a radically 

 Dew direction to introduce the prosecution of inves- 

 tigation per se ; and it should be well considered 

 where this begins, and whether it is the proper func- 

 tion of the government to prosecute such work. 

 The establishment of a teaching university is a still 

 greater step. 



There is further, in my opinion, no need of a 

 university in Washington, as we already have as 

 good an institution as could be wished at the neigh- 

 boring city of Baltimore. 



An appeal to the prestige of the names of the 

 statesmen of the early days of the country is always 

 to be deprecated. We are suffering at the present 

 time from a law passed under the hurrah raised by a 

 similar appeal. L. S. 



Some points in the evolution of the horses. 



The main facts with regard to the evolution of 

 the horses have long been known, and the series of 

 modifications in the limbs, skull, and molar teeth, so 

 fully described, that little doubt remains as to the 

 various links in the long chain. But, in tracing out 

 the line of descent of any group of organisms, it is 

 not only necessary to follow out the steps of progres- 

 sion in a general way, but in all their details. In 

 the case of fossils, this must, for the most part, be 

 done by many different observers, as so much depends 

 upon the fortunate discovery of good specimens. The 

 present note gives a small contribution of this kind to 

 the elucidation of the history of the horses. 



The earliest member of the series of which we 

 know much is the Hyracotherium of Owen (Oro- 

 hippus, Marsh). This little animal is quite abundant 

 in the lower eocene of Wyoming, and has been very 

 fully described by Professor Cope. In this genus 

 (fig. 1) the incisors are arranged in a semicircle, 



Fig. 1. — Lower incisor and Fig. 2. — Lower incisor and 

 canine series of Hyracothe- canine series of Anchithe- 

 rium (after Cope). One-half rium (after Kowalewsky). 

 natural size. 



either uninterruptedly or separated by slight inter- 

 vals. They are simple teeth, with sharp, chisel- 

 shaped crowns. The canines are small, conical, and 

 everted. The symphysis of the lower jaw is long 

 and much contracted, rounded and somewhat ex- 

 panded at the end. 



The next type in the series is the Mesohippus of Pro- 

 fessor Marsh, from the White Eiver beds or lower mio- 

 cene. Although the characters which Professor Marsh 

 gives as separating this form from Anchitherium are 

 either inaccurate or not of generic value, Mesohippus 

 must, as we shall presently see, be regarded as a dis- 

 tinct genus. Here the shape of the mandibular 

 symphysis and of the incisor teeth is v^ry much as 

 in Hyracotherium. The incisors are small, with 



rather broad, chisel-shaped crowns, and without a 

 trace of an invagination of the enamel. The advance 

 from Hyracotherium to Mesohippus consists chiefly 

 in the increased size of the animal, reduction of the 

 number of digits, greater complexity of the premolar 

 and molar teeth, and enlargement of the brain. 

 Specimens of Mesohippus with the incisors in posi- 

 tion are rather rare. The description given above 

 is of a small species (No. 10,246 of the Princeton 

 museum) which was obtained by the Princeton scien- 

 tific expedition of 1878 at Chalk Bluffs, Colorado. 



In the upper miocene deposits of the Pacific coast 

 the true Anchitherium (Miohippus, Marsh) appears. 

 In this genus the incisors show an invagination of 

 enamel on the grinding surface of the crown. The 

 pit so formed is shallow, and comparatively soon 

 wears down to a scar. I have not had an opportunity 

 of examining European specimens with reference to 

 this point, but the presence of the pit is clearly shown 

 in Kowalewsky's figures {Memoires de Vacademie 

 imper. de St. Petersbourg, 7th ser. tome xx. pi. iii. 

 figs. 55 and 57). Of fig. 57 (see fig. 2), Kowalewsky 

 says, " Les incisives mitoyennes presentent deja. les 

 puits en email qui sont si characteristiques pour les 

 chevaux." This pit, seen in its earliest stages in 

 Anchitherium, goes on increasing until it reaches its 

 greatest development in the recent genus Equus. It 

 is of interest to see that even in this small and com- 

 paratively unimportant detail w r e find a fresh confir- 

 mation of the accuracy of previously expressed views 

 as to the series of equine ancestors. If these deter- 

 minations are accurate, they must, of course, hold 

 good down to the minutest details. Further inves- 

 tigation will undoubtedly bring more of these minor 

 correspondences to light. W. B. Scott. 



Geol. mus., Princeton, N.J., Dec. 16. 



Equatorial currents in star and planetary atmos- 

 pheres. 



In the 1 Astronomical notes' contained in the num- 

 ber of Science for Dec. 11, occurs a statement in 

 regard to the circulation of the earth's atmosphere 

 which seems to me to require qualification, and I 

 therefore venture to call your attention to it. The 

 passage in question reads as follows : "As to the 

 earth, we know that the general drift of the lower 

 atmospheric currents is eastward, rotating faster 

 than the globe itself ; but of the circulation high up 

 above the clouds we knew absolutely nothing until 

 the red sunsets following the Krakatoa outburst 

 . . . indicated, by their successive appearances at 

 different places, a probable upper equatorial current 

 moving rapidly westward, i.e., rotating slower than 

 the earth." 



Now, it is well known that the eastward move- 

 ment of the atmosphere is confined to the temperate 

 zones, and is not observable in the polar or tropical 

 regions. On the contrary, the most striking feature 

 in the circulation of the atmospheres is the great 

 equatorial wind-current which flows from east to 

 ivest along the equator, and is felt beyond the tropics 

 of Capricorn and Cancer. It is about 60° in width, 

 and therefore covers one-half the earth's surface. 

 It is also, as I believe, the most important factor in the 

 whole system of oceanic and atmospheric circulation, 

 since, by the friction of its movement over the ocean 

 surface, it produces the great equatorial water-cur- 

 rent which is the chief, though not the only, cause of 

 all the great movements of oceanic waters. The 



