426 



THE POPULAR SCIENCE MONTHLY. 



if it cracks, that it has been bleached too 

 much. The thickness of paper can be meas- 

 ured by putting a number of leaves together, 

 or by the micrometrical determination of 

 the effect of adding a single leaf to the 

 mass. We may bum the paper and exam- 

 ine the ashes. If they amount to more than 

 three per cent, clay, kaolin, spar, or gypsum 

 has been added to the pulp. When we 

 color paper with an iodine solution, yellow 

 indicates the presence of wood-fiber ; brown, 

 of cotton or linen ; and the absence of color- 

 ation, of cellulose. 



Man's Agency in the Extermination of 

 Species. — Extermination is defined in Nature 

 as indicating that in certain parts of the 

 range of a species, whether plant or animal, 

 it has ceased to exist, however abundant it 

 may remain elsewhere ; while in other cases, 

 especially if the species have but a limited 

 distribution, it easily becomes equivalent to 

 extirpation. The older school of zoologists 

 seem hardly to have contemplated the possi- 

 bility of a whole species having become ex- 

 tinct within the period since man appeared 

 upon earth, or to have supposed that a species 

 could by human efforts be utterly swept away. 

 Thus there was once skepticism about the ex- 

 tinction of the dodo, or, that having been es- 

 tablished, about its having existed within the 

 human period. The disappearance of numer- 

 ous animals, formerly abundant, from the set- 

 tled parts of our country, affords examples 

 of local extinction ; and the fate of the buf- 

 falo threatens to furnish an instance of total 

 extinction by the agency of man. Man's 

 agency usually acts indirectly — as by chang- 

 ing the conditions of the country, so as to 

 make them unfavorable to the subsistence of 

 certain animals, rather than directly by kill- 

 ing all the individuals of a species outright. 

 The wolf has defied all efforts, by offering 

 bounties and otherwise, to accomplish its 

 destruction in Europe, except in artificially- 

 built-up Holland, where it never was at 

 home ; Denmark, every spot of which is ac- 

 cessible to the hunter ; and the United King- 

 dom, where its forest resorts have been re- 

 moved. Other instances are the extirpation 

 of the quail in New Zealand by means of 

 fires that were lighted for other purposes ; 

 the threatened destruction of other interest- 

 ing animals of Australia and New Zealand 



by animals of the weasel kind that were in- 

 troduced to prey upon the imported rabbits ; 

 and the destruction of turkey-buzzards' eggs 

 and petrels in Jamaica by the mongooses that 

 were taken there to make war upon rats ; of 

 the Diablotin petrel of Dominica by a spe- 

 cies of opossum ; and the destruction of the 

 cahoivs in the Bermudas, till it is not known 

 now whether the bird exists there. The 

 great skua, or " bonxie," disappeared from 

 one of its three breeding - stations in the 

 Shetland Islands several years ago, and has 

 been maintained at the other two only through 

 the vigorous exertions, to repress poachers 

 and preserve it, of the late Dr. Robert Scott 

 and the late Dr. Lawrence Edmondston, re- 

 spectively. The Zoological Society has or- 

 dered medals struck in honor of the serv- 

 ices these gentlemen rendered to science. 

 Though the reward is posthumous, and goes 

 to the heirs of the well-doers instead of to 

 themselves, the acknowledgment is a fitting 

 one, marks an example, and is an encourage- 

 ment to the lovers of living nature. 



Prof. Wright in the British Association. 



— Prof. G. F. Wright's paper in the British 

 Association, on The Ice Age of North Amer- 

 ica and its Connection with the Appearance 

 of Man on that Continent, is spoken of in 

 Nature as a most interesting one. The au- 

 thor said that the glacial deposits, trans- 

 ported from several centers mostly outside 

 the Arctic Circle, and the absence of a polar 

 ice-cap, militated against an astronomical 

 and for a geographical cause of the great 

 cold, particularly as an uplift of the glaciated 

 area was coincident with an important subsi- 

 dence in Central America. He regarded the 

 so-called " terminal moraine of the second 

 period " as a moraine of retreat due to the 

 first glaciation, and thought that the evi- 

 dence of forest beds, mainly to the south of 

 the area, indicated local recessions of ice, 

 and not a single great interglacial epoch. 

 Palaeolithic remains similar to those of the 

 Somme and Thames have been found in sev- 

 eral irravel terraces flanking streams which 

 drain from the glaciated region, and made 

 up of glacier-borne detritus ; they arc re- 

 garded by the author as deposits of the 

 floods which characterized the closing por- 

 tions of the Glacial period. The recession 

 of the falls of Niagara and St. Anthony 



