September 22, 1904] 



NA TURE 



521 



tjuite in harmony with the multiple origin of the historic 

 and recent races of horses as recently established by Profs. 

 Ridgeway and Ewart. The Pliocene horse of America still 

 requires further exploration before it can be positively 

 aftirmed either that all the links to Equus are complete or 

 Chat America is indubitably the source of this genus. The 

 J-o\ver Pleistocene of America exhibits a great variety of 

 races, ranging in size from horses far more diminutive than 

 the smallest Shetland to those exceeding the largest modern 

 •draught breeds — yet ail these races became extinct, and 

 did not survive into the human period as was the case in 

 .South America. The relations of these North American 

 races to those of South America and of .•\sia and Africa is 

 •a subject requiring further investigation. 



The address was illustrated by photographs of a large 

 series of models, of osteological preparations showing the 

 mechanism and breeds of the horse, and of the mounted 

 fossil specimens recently discovered. 



Prof. Ewart referred to the fact that in pre-Glacial times 

 (here were several distinct species of EquidiE in the New 

 World, and that one of the objects of present inquiry is 

 to connect the recent Equid^ with these or other extinct 

 forms. Before it is possible to point out the connection 

 between the true horses and the pre-Glacial or Pleistocene 

 horses it is necessary to determine the number of species 

 and varieties of the horse now extant. He described at 

 some length Prjevalsky's horse, the Norse type of horse 

 still found fairly pure in the north-west of Scotland, and the 

 recently discovered Celtic pony. He referred to Prjevalsky's 

 horse as the least specialised of living Equidse, as evidenced 

 In the character of its mane and tail and the presence of 

 a complete set of callosities, and he discussed the question 

 as to whether it is a mule or simply the offspring of 

 Mongolian ponies run wild. The Norse type of horse differs 

 from Prjevalsky's in its heavy mane and tail, finer head, 

 and smaller ears. The Celtic pony is the most specialised 

 of living Equidie, as shown by the absence of such vestiges 

 as fetlock-pads and chestnuts from the hind legs, and the 

 presence of a peculiar tail-lock which adapts it for a sub- 

 arctic habitat. Phot9graphs were shown to illustrate these 

 \arious features. 



Prof. Ridgeway then stated some of the evidence which 

 led him to conclude that a distinct species or variety of the 

 horse had been specialised in North .i\frica. Darwin sup- 

 posed that not only was the .\rab horse the result of 

 artificial breeding by the Arabs, but that the dark colour 

 of the English racehorse was due to the Arab dislike of 

 light coloured horses. History puts it beyond doubt that 

 the .\rabs had no horses at the beginning of the Christian 

 era, and that they obtained their famous breed from North 

 .Africa, and, so far from their disliking light coloured horses, 

 they have a predilection, on religious grounds, for white 

 or grey horses, as had the Germans, Greeks, and Romans. 

 Bay and other dark coloured horses were well known in 

 northern Africa and western Asia many centuries before the 

 Arabs owned horses. The horse appears for the first time 

 on Egyptian monuments about 1500 B.C., and is almost 

 always painted brown, and those ridden by Libyans and 

 depicted on pottery (at Daphne, B.C. 660-570) are always 

 painted dark. These horses were not imported into northern 

 -Africa from .Asia ; on the contrary, Solomon (tenth century 

 B.C.) and his neighbours imported horses from Egypt which 

 must have been of a superior race. These horses were 

 obtained from the Libyan tribes (as none of the other peoples 

 in that region possessed them), and from them also came 

 those of southern Spain, the ancestors of the Andalusian and 

 Pampas horses. The Libyan horses passed into Sicily and 

 southern Italy, and in the games of Greece and in Roman 

 times they were the fleetest known. The bay horse there- 

 fore not only belongs to Africa from the earliest times, but 

 was then, as now, the swiftest. The Libyan horses show 

 a greater tendency to stripes than do Asiatic horses, and 

 the former often lack hock callosities, which are present 

 .ind of large size in coarse Asiatic horses. The tail of the 

 Libyan horse differs in structure, covering, and carriage 

 from that of Asiatic horses ; the hoofs are longer, and the 

 neigh is different. Libyan horses were docile, and could be 

 ■driven without bit, while the peoples who used Asio- 

 European horses invented the bit. Prof. Ridgeway con- 

 cludes that Equus caballus libicus is to be regarded as a 

 distinct varietv. 



THE ACTION OF WOOD ON A PHOTO- 

 GRAPHIC PLATE IN THE DARK.' 

 TT has been shown in former papers that many substances 

 are capable of acting on a photographic plate in the 

 dark and producing a picture of themselves. Further in- 

 vestigation shows that this property belongs probably to all 

 woods, some, however, being much more active than others. 



To obtain a picture the wood has to be in contact or at 

 a little distance above the photographic plate, and has to 

 remain there for times varying from half an hour to eighteen 

 hours, and to be at a temperature not higher than 55° C. 



The wood of the conifers is very active, and gives pictures 

 which are very definite. Fig. i is a pictifre of a section 

 of a branch of a Scotch fir, and shows well the rings of 

 spring and autumn growth. It is remarkable that the 

 former are very active, producing in this picture the dark 

 rings, and so with the other pictures, the part which is 

 active in the original is dark in the picture. The rings 

 seen in the wood are very sharp and strongly pronounced 

 in the picture. If the action e.xerted on the plate be owing 

 to the presence of hydrogen peroxide, as has been previously 

 suggested, no doubt it is produced by the resinous bodies 



present in the wood, but it is remarkable that there is no 

 action from the dark autumn wood. Experiments described 

 in the full paper show that resin exists in the dark rings, 

 but apparently under such conditions that it cannot escape. 

 Other members of the pine group have been experimented 

 with and have been found to behave in the same way as 

 the Scotch fir. 



With the spruces the action on the plate is not so definite 

 and well marked ; the white wood is always active, but in 

 some cases the dark rings are also active, and the pictures 

 are not so sharp as with the firs. Larch wood gives a very 

 interesting result, for the picture is the reverse of that of 

 the Scotch fir, that is, the dark rings in the wood are the 

 active rings and the light rings are inactive. 



With regard to woods other than conifers, oak and beech 

 are both active and give very good pictures, so also does 

 acacia (Robinia), Spanish chestnut, and sycamore; on the 

 other hand, ash, elm, horse chestnut, plane are comparatively 

 but slightly active. In the full paper lists of woods are 

 arranged according to their activity. 



Many foreign woods are very active, but as the annual 

 rings are often not well developed, the pictures they give 

 are of a somewhat different character. The African black 

 wood, rose wood, cocobola, and many others are very active. 

 Several of the foreign woods have a ring of white wood 

 which is quite inactive. 



I By Dr. William J. Russell, F.R.S. Read before the Royal Society, 

 June .6. 



NO. 1 82 I, VOL. 70] 



