February 27, 1896] 



NATURE ^ 



39] 



that De Saussure is the author of the term ; but I have long 

 been foiled by its omission from the index of the famous 

 "Voyages dans les Alpes." In " Open- Air Studies," however, 

 I ventured to compare the mammillations of a glaciated surface 

 to those upon an antique wig ; but all the time, it seems, Mr. 

 Whymper held the key of the matter for us, in a passage which 

 has escaped the memory even of Prof. Bonney (see "Ice- 

 Work," 1896, p. 10). Mr. Whymper, in fact (" Scrambles 

 amongst the Alps," fourth edition, 1893, p. 133), supplies the 

 reference to De Saussure ; and in the " Voyages dans les Alpes," 

 1804, tome ii. p. 435, par. 1061, we may read of what are styled 

 in the margin " montagnes moutonnees." De Saussure states 

 that behind Envionne (the modern Envionnaz), in the upper 

 valley of the Rhone, " ces rondeurs contigues et repetees 

 forment en grand I'effet d'une toison bien fournie, ou de ces 

 perruques que Ton nomme aussi moutonnees." In face of this, 

 there is no longer any need to tax the credulity of our pupils 

 with a fanciful explanation, which we seem to have forced 

 even upon French-speaking peoples. 



Grenville a. J. Cole. 

 Royal College of Science for Ireland, 

 Dublin, February 17. 



The Age of the Present Canadian Flora. 



Prof. D. P. Penhallovv has recently identified some frag- 

 ments of wood found in the Leda clays of Montreal, as Picea 

 nigra, the common black spruce. This is another addition to 

 the group of plants which represent our present knowledge of 

 the flora of Canada in Pleistocene times. This Pleistocene flora 

 may now be taken to include not merely the plants found in 

 these Leda clays and in the clays believed to be equivalent to 

 them in age in Ontario, but also the ancestors of the present 

 inland maritime flora found on the shores of the Great Lakes, 

 hundreds of miles from the sea-coast, and of the plants which 

 are common to Europe and America, and which include so 

 many arctic and sub-arctic, as well as northern temperate 

 species. The inland maritime plants, and probably also the 

 sub-arctic species now found so far south as the headlands of 

 Lake Superior, made their way to their present localities during 

 the deposit of the Leda clays when a considerable part of Eastern 

 Canada was submerged. Six of the species which occur in the 

 Leda clays at Ottawa and Montreal, and thirteen of the inland 

 maritime plants, as well as several of the Lake Superior sub- 

 arctic species, are also European, showing that at that period 

 the intermingling of the American and European floras was well 

 established, but leaving open the possibility of these plants 

 common to the two continents being even older than the period 

 of the Leda clays. 



The intermingling of the Asiatic and American floras appears 

 10 have taken place at a still earlier period. The oldest known 

 representatives of the existing Canadian flora are those few iden- 

 tical species found by Mr. Lester F. Ward in the Laramie rocks 

 of the Western United States — rocks which Sir William Dawson 

 refers to the Lower Eocene. Two of those identified now 

 occur in both Japan and Canada ; and one, still living in Japan, 

 has, if correctly identified, become extinct on the American 

 continent. Again, among the Leda clay and inland maritime 

 plants there are several species which are likewise common to 

 the two countries. The intermingling of Asiatic and American 

 plants evidently took place prior to the upheaval of the Rocky 

 Mountain chain, as the extensive flora peculiar to British 

 Columbia, Oregon, and southward, is almost without a repre- 

 sentative in Japan. This British Columbia flora, so well repre- 

 sented by various species of Claytonia, Lupinus, Trifolium, 

 Astragalus, Saxifraga, &c., as well as Coniferae, is of more 

 recent birth — probably Later Tertiary and Post-Tertiary. 



The most recent creations in Canada would appear to be the 



plants which— well represented by Composita^ an order of no 



great antiquity — are now so marked a feature of the prairies 



of Manitoba and the surrounding country — prairies which in 



line places are still in process of formation. 



A. T. Dru.mmond. 



Children's Drawings. 



With regard to young children drawing upside down, I have 

 for some time past collected observations. It is certainly true, 

 that a great many children do draw in this way ; on the other 

 hand, many from the first draw the right way up. I have seen 



NO. 1374, VOL. 53] 



a boy of four, when asked to draw a rook on a haystack, begin 

 at the bottom of the paper with the rook's back, and gradually 

 work his way up to the haystack ; he then turned it round, and 

 handed it to me to look at, evidently realising that it was 

 inverted. 



I do not think the explanation depends in any way on the 

 inversion of the retinal image. If a child, who draws upside 

 down when drawing on a horizontal table, is asked to draw on a 

 blackboard placed vertically, he will draw everything the right 

 way upwards. It seems to me, that the explanation simply is 

 that the child has to draw an object, which he has seen in a 

 vertical plane, on paper placed in a horizontal plane — an 

 extremely difficult task to him — and it is a mere question of 

 convenience to him at which end.he begins, .both being equally 

 wrong from his point of view. This will also explain why children 

 sometimes look at picture-books upside down, and also why 

 small children are much more ready to draw objects, which they 

 have been accustomed to see in a horizontal plane, such as a 

 plate with oranges on it, than an erect object. 



The Old Palace, Richniond. Rina Scott. 



..^ LA . •• ■ , 



THE" R'dNTGEN RA YS. 



'X'HE discovery by Prof. Rontgen of the rays which 

 ■'■ bear his name has aroused an interest perhaps 

 unparalleled in the history of physical science. Reports 

 of experiments on these rays come daily from laboratories 

 in almost every part of the civilised world. A large part 

 of these relate to the fnethods of producing Rontgen 

 photographs, and the application of the " new photo- 

 graphy " to medical and other purposes. A considerable 

 amount of work has, however, been done on the physical 

 properties of these rays ; this has entirely confirmed 

 the results stated by Rontgen in the paper in which he 

 announced his discovery. The freedom of refraction of 

 these waves, in which they are different from ordinary light, 

 has been the subject of direct experiments made by M. 

 Perrin and by Dr. Joly, while Dr. Lodge and others have 

 confirmed the absence of any deflection in the magnetic 

 field which diflferentiates these rays from the ordinary 

 kathode rays. 



Up to the present, however, no phenomena have been 

 observed which enable us to say whether these waves 

 are or are not transverse vibrations of very small wave- 

 length, longitudinal vibrations, or even vibrations at all. 

 Nothing of the nature of polarisation or of interference 

 has been described. The absence of polarisation can at 

 the present stage of the investigation hardly be pressed as 

 an argument against these rays being transverse vibrations. 

 For, of the three methods of producing polarisation in light 

 — reflection, refraction, and absorption — only the latter is 

 available for these rays. Now the number of substances 

 which produce sensible polarisation in ordinary light by 

 absorption is very small, and unless a much larger 

 number possess this property for the Rontgen rays, it is 

 hardly likely that, even if there are such substances, they 

 would have been discovered in the three months which 

 have elapsed since the publication of Rontgen's dis- 

 covery. I may remark that I have made a large number 

 of experiments on the opacity to these rays of plates of 

 tourmaline (i) with their axes crossed, (2) with their axes 

 parallel, testing the intensity of the rays which came 

 through in some cases by their action on a photographic 

 plate, in others by the discharge they produced in an 

 electrified plate on which they were incident. The result 

 of these experiments was entirely negative, for although 

 the tourmaline plates produced very considerable absorp- 

 tion of the rays, no difference was detected between the 

 absorption when the axes were crossed and when they 

 were parallel. It is very desirable that a large number of 

 substances should be tested in this way. 



M. C. Henri has made the very interesting observation 

 that «an opaque coin coated with the phosphorescent 

 sulphide of zinc will allow these rays to pass through it ; 

 the details of this experiment will be received with much 



