July 4, 1901] 



NA TURE 



243 



Oregon, invest it with an exceptional interest, in relation to the 

 question of the probable limitations in distribution of the 

 animals and plants peculiar to these ; and in the end the unex- 

 pected result has been obtained that, although the gap between 

 the Shasta and the Cascades is far less than between it and the 

 Sierra Range, and while plants and animals representative of 

 both ranges are present upon it, the Sierra species are pre- 

 dominant. 



In the course of the expedition names were given to newly- 

 discovered peaks and canyons, and at points in the ascent 

 favourable for work and observation individual members of the 

 exploring party were left encamped, in one case for a period 

 of well-nigh a couple of months. The net result biologically 

 has been the discovery of five new species of plants, eight of 

 mammals. 



The Report opens with a description of the general features 

 of the mountain ; and its glaciers, basins, canyons, streams, 

 slopes, timber-lines, and other natural features, are in turn 

 dealt with in an amply and beautifully illustrated manner. 



There then follows a systematic report upon the forest trees 

 and a description of the life zones above 5500 feet, that being 

 the altitude of limitation of the " transition zone " of the 

 mountain, the facies of which are those of the surrounding 

 country. The fauna and flora of this are given, and the super- 

 posed heights are next dealt with under zones as follows : the 

 Canadian zone, of 2000 feet, which is defined as a " continuous 

 forest of stately trees " ; the Hudsonian, also of 2000, the 

 highest of the timber-belts, characterised by the presence of but 

 two species of trees — a hemlock and a white-bark pine ; and 

 the Alpine zone, or that occupying the interval between the 

 timber-line and upper limit of plant growth. 



The fauna and flora of each of these are in turn given in full 

 in the form of classified lists of species. Then follows a dis- 

 cussion, with comparison, of the boreal flora and fauna of 

 Shasta and the Sierra and Cascades, again with classificatory 

 lists, and of the surrounding gaps and rivers, regarded as 

 barriers to boreal species. The greater part of the Report which 

 remains consists of a systematic list of the mammals and birds 

 of the area, arranged in order of classification, with full diagnoses 

 and measurements, and " remarks " which embody interesting 

 observations on the habits of more especially the burrowing 

 animals. There follows a chapter on the distribution of the 

 Shasta plants. Concerning the zoological synonymy, many who 

 are familiar with Dr. Merriam's work will be prepared for sub- 

 species and what we in Europe are apt to regard as splitting. 

 In this Report there is little of it, and when the richness of 

 the materials which Dr. Merriam and his contemporaries 

 usually command is borne in mind, criticism of this order were 

 best left in abeyance. In the course of the strictly zoological 

 portion of the Report several new text illustrations are introduced, 

 and any more life-like and fascinating than those of the Rock 

 Cony (Ochotona \^Lagoiiiys'\), the ^VmV^Littfeola) and Marten, 

 or among the birds, of the Red Tail and the Clark Crow it 

 would be difficult to imagine. 



Shasta is characterised by nothing better than its scanty 

 nioisture, and the effect of this on the plant population and zonal 

 distribution is fully discussed. We have nought but the highest 

 praise for this Report. It fills us with envy and arouses feelings 

 of mute admiration for the enterprise of Dr. Merriam and his 

 co-workers in the field. It is worthy the nation that will levy 

 a tax to aid in the foundation and maintenance of a university, 

 and where wealth, long lavished on scientific exploration of 

 the land of their birth, is now bringing its reward of commercial 

 prosperity. 



THE NADIR OF TEMPERATURE AND 

 ALLIED PROBLEMS.^ 



T~)ETAILS are given in this paper which have led to the 

 following results : — 

 The helium thermometer which records 2o'-5 absolute as the 

 boiling point of hydrogen, gives a; the melting point 16' abso- 

 lute. This value does not differ greatly from the value previously 



}}-}'> Physical Properties of Liquid and Solid Hydrogen. (2) Separation 

 of i ree Hydrogen and other Gases from Air. (3) Electric Resistance 

 Thermometry at the Boihng Pomt of Hydrogen. (4) Experiments on the 

 Liquefaction of Helium at the Melting Point of Hydrogen. (5) Pyro- 

 jjectncity, Phosphorescence, So. The Hakerian Lecture delivered at the 

 Royal Society on June 13, by Prof. James Dewar, F.R S. 



NO. 1653, VOL. 64] 



deduced from the use of hydrogen gas thermometers, viz., 

 l6'7. The lowest temperature recorded by gas thermometry 

 is I4''5, but with more complete isolation and a lower pressure 

 of exhaustion, it will be possible to reach about 13" absolute, 

 which is the lowest, temperature that can be commanded by the 

 use of solid hydrogen. Until the experiments are repeated with 

 a helium gas thermometer filled at different pressures, with the 

 gas previously purified by cooling to the lowest temperature 

 that can be reached by the use of solid hydrogen, no more 

 accurate values can be deduced. 



The latent heat of liquid hydrogen about the boiling point as 

 deduced from the vapour pressures and helium-thermometer 

 temperatures is about 200 units, and the latent heat of solid 

 hydrogen is about i5 units. 



The order of the specific heat of liquid hydrogen has been 

 determined by observing the percentage of liquid that has to be 

 quickly evaporated under exhaustion in order to reduce the tein- 

 perature to the melting point of hydrogen, the vacuum vessel in 

 which the experiment is made being immersed in liquid air. It 

 was found that in the case of hydrogen the "amount that had to 

 be evaporated was 15 per cent. This value, along with the 

 latent heat of evaporation, gives an average specific heat of the 

 liquid between freezing and boiling point of about 6 When 

 liquid nitrogen was similarly treated for comparison, the result- 

 ing specific heat of the liquid came out 0'43 or about 6 per atom. 

 Hydrogen therefore follows the law of Dulong and Petit, and 

 has the greatest specific heat of any known substance. 



The same fine tube used in water, liquid air, and liquid 

 hydrogen gave respectively the capillary ascents of 1 5 '5, 2 and 

 5 '5 divisions. The relative surface tension of water, liquid air 

 and liquid hydrogen are therefore in the proportion of 15 '5, 2, 

 o'4. In other words, the surface tension of hydrogen at its 

 boiling point is about one-fifth that of liquid air under similar 

 conditions. It does not exceed one thirty-fifth part the surface 

 tension of water at the ordinary temperature. 



The refractive index of liquid hydrogen determined by 

 measuring the relative difference of focus for a parallel beam 

 of light sent through a spherical vacuum vessel filled in succes- 

 sion with water, liquid oxygen and liquid hydrogen, gave the 

 value I '12. The theoretical value of the liquid refractive index 

 is I'll at the boiling point of the liquid. This result is 

 sufficient to show that hydrogen, like oxygen and nitrogen in 

 the liquid condition, has a refractivity in accordance with 

 theory. 



Free hydrogen, helium and neon have been separated from 

 air by two methods. The one depends on the use of liquid 

 hydrogen to boil the dissolved gases out of air kept at a tem- 

 perature near the melting point of nitrogen'; the other on a 

 simple arrangement for keeping the more volatile gases from 

 getting into solution after separation by partial exhaustion. By 

 the latter mode of working something like i/34000th of the 

 volume of the air liquefied appears as uncondensed gas. The 

 latter method is only a qualitative one for the recognition and 

 separation of a part of the hydrogen in air. In a former paper 

 on the " Liquefaction of Air and the Detection of Impurities " 

 [Chem. Sac. Proc, 1S97), it was shown that 100 c.c. of liquid 

 air could dissolve 20 c.c. of hydrogen at the same temperature. 

 The crude gas separated from air by the second method gave on 

 analysis— hydrogen 32 '5 per cent., nitrogen S per cent., helium, 

 neon, &c., 60 per cent. After removing the hydrogen and 

 nitrogen the neon can be solidified by cooling in liquid hydrogen 

 and the more volatile portions separated. 



There exists in air a gaseous material that may be separated 

 without the liquefaction of the air. For this purpose air has to 

 be sucked through a spiral tube filled with glass wool immersed in 

 liquid air. After a considerable quantity of air has been passed, 

 the spiral is exhausted at the low temperature of the liquid air 

 bath. The spiral tube is now removed and allowed to heat up 

 to the ordinary temperature, and the condensed gas taken out 

 by the pump. After purification by spectroscopic fractionation, 

 the gas filled into vacuum tubes gives the chief lines of xenon. 

 The spectroscopic examination of the material will be dealt 

 with in a separate paper by Prof. Liveing and myself. A 

 similar experiment made with liquid air kept under exhaustion, 

 the air current allowed to circulate being under a pressure 

 less than the saturation pressure of the liquid to prevent 

 liquefaction, resulted in crypton being deposited along with the 

 xenon. 



A study of fifteen electric resistance thermometers as far as 

 the boiling point of hydrogen has been made, and the results 



