146 



SCIENCE 



[N. S. Vol. XXVI. No. 657 



Problems of the Development of Nerves," by 

 Koss Granville Harrison. When the rudiment 

 of the limb of a tadpole is transplanted it 

 acquires after a time nerves which are con- 

 nected with the nerves of the region of im- 

 plantation. The nerves have the same arrange- 

 ment and distribution as those of the limb 

 in its natural position. This is the case even 

 in limbs taken from individuals which have 

 undergone their development after having 

 been deprived of their nervous system and 

 also in the accessory limbs which sometimes 

 bud out from the transplanted appendages. 

 The nerves in question are not preformed in 

 the transplanted limb but they actually grow 

 into it, their mode of distribution being de- 

 termined by the structures within the latter. 

 The development of an embryonic nerve 

 ceases and degeneration sets in as soon as the 

 connection with its ganglion is severed. 



SOCIETIES AND ACADEMIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 193d meeting of the society was held 

 on May 8, 1907, Vice-president Campbell in 

 the chair and sixty-two members present. 

 Under the head of informal communications 

 Mr. F. E. Wright exhibited artificial crystals 

 of silver, copper and diopside produced under 

 various conditions in the Geophysical Labora- 

 tory of the Carnegie Institution of Washing- 

 ton and discussed briefly the bearing of the 

 difPerent modes of formation on the general 

 theory of the precipitation of native copper 

 and silver ores. Mr. Lawrence La Forge ex- 

 hibited a new orthorhombic pyroxene found in 

 a slag at Bingham, Utah. Although this min- 

 eral was found by Mr. Wirt Tassin, of the 

 National Museum, to have the chemical com- 

 position of a normal calcium iron pyroxene, 

 crystallographically it was found by Mr. La 

 Forge to be orthorhombic but with the same 

 prism angle within the limits of error as 

 ordinary monoclinic pyroxene. Six different 

 crystal forms in all were observed, the prevail- 

 ing habit being that of an elongated square 

 prism, termination either by the base or by an 

 oscillatory combination of the base and a 

 hracydome. An attempt was made to deter- 



mine the optical constants but was unsuccess- 

 ful because of the dark color of the mineral 

 and shattered condition of even very small 

 crystals. Two sections, however, were ground 

 thin enough to determine the extinction, which 

 was found to be parallel and the orthorhombic 

 character thus confirmed. 



Regular Program 

 The New Map of the Yosemite Valley: F. E. 



Matthes. 



This topographic sheet of the U. S. Geolog- 

 ical Survey, about to be published, affords a 

 particularly instructive example of modern 

 detail mapping, in that it suggests possible 

 criteria for the guidance of the topogTapher 

 in the consti-uction of maps which shall em- 

 body a scientific interpretation of the relief. 



The value of a map as a means of repre- 

 senting land forms depends upon two factors: 

 selection of scale and contour interval, and 

 ability on the part of the map maker to ex- 

 press topographic character. The latter pre- 

 requisite will not be considered in this discus- 

 sion. Thus far the factors which have been 

 determinative in the selection of proper scale 

 and contour interval have, as a rule, been : 

 purpose for which the map is made; degree of 

 cultural development of region mapped; cost 

 per square unit; funds available, etc. Definite 

 physiographic criteria have not yet been con- 

 sidered in this connection although the present 

 state of physiographic knowledge is such that 

 the attempt to apply physiographic principles 

 to the mapping of land fonns seems opportune 

 and justified.^ Most topographic maps give 

 little more than an imperfect, incomplete pic- 

 ture of the relief. Others again are over- 

 burdened with unnecessaiy, irrelevant details. 

 Some actually amount to misrepresentations, 

 even though they be the product of sincere 

 and painstaking effort. The topographer is 

 to-day and always has been more or less un- 

 certain as to the matter of detail. Both in 

 the selection of scale and contour interval, 

 and in the actual field sketching he is at a loss 

 to decide which of the smaller topographic 

 units he must show, and which he must leave 



