138 



NATURE 



[March 31, 1921 



Geograph. Soc, December, 1866). I would have pro- 

 ceeded by the head of the Tambur River, with 

 Hooker as my guide — made the attempt, at any rate, 

 and, failing in that route in Nepal, taken that of the 

 Doukia La and got on to the Arun drainage as soon 

 as possible. 1 would have gone, preferably alone, 

 with a very small establishment of hillmen, Lepchas 

 or Bhutias— men who know something of the 

 country and of the habits of the people. It is essential 

 also to have a man of position and rank with the 

 party; success depends greatly on him. 



I would have taken a very limited store of pre- 

 served food, trusting as much as possible to the 

 country for all supplies for my men and myself. 

 Sheep are always procurable ; on the Pangkong I 

 lived solely on mutton and the few birds I shot. At 

 that time I had an invaluable man as chuprasie and 

 interpreter ; he had come with me from Ladak. Born 

 at Leh, his father was a Kashmiri merchant and his 

 mother a Ladaki. He spoke Hindustani, Punjabi, 

 and Tibetan ; he had the assurance and manner of the 

 Indian, with a knowledge of the religion and habits 

 of his mother's race. His religion, Mohammedan, 

 sat lightly upon him, and he was quite at home 

 among Buddhists. 



The survey work over a large area is easy, but 

 some of it must be stiff, particularly w'here the 

 descent off the high plateau commences. The 

 accurate fixing of stations in advance will necessitate 

 going over much ground and take time, for trigo- 

 nometrical points are few. The base of my work in 

 1863 would have been in Sikkim, since all surveyed. 

 The present base is the frontier itself, and I fancy 

 a large area of this is known north of Chumbi. It 

 is really only one man's work. To show this, I 

 put on record here how the topography of the Kashmir 

 territory was done, and refer anyone interested to 

 my paper read before the Royal Geographical Society 

 on January 11, 1864, with a map of Baltistan attached. 

 This covers some 4000 square miles plane-tabled in 

 the summers of i860 and i86i- — a most difficult, lofty, 

 and glaciated country, entailing much climbing. 



The Duke of the Abruzzi had this map to guide 

 him when he made his expedition to the great Baltoro 

 glacier. This glacier I was fortunate to be the first 

 European to see and follow up to the base of the 

 second highest peak in the Himalayas, and I was 

 then within seventeen miles of the summit. 



Having spent the best years of my life on the Hima- 

 layas or in sight of them, and collected and written 

 on the fossil and recent fauna, I naturally take a 

 deep interest in the exploration of Tibet which now 

 seems possible. I should be sorry to see any difficulty 

 arise, political or otherwise. 



We are living in an extravagant age. Nothing ap- 

 parently can be done except on a vast scale ; more is 

 spent than need be. The size of the expedition may 

 frighten the Tibetans and lead to difficulties, as it did 

 before when another large expedition was to have 

 entered the country. H. H. Godwin-Austen. 



Nore, Godalming, Surrey, March 16. 



Molecular Size and Range of Molecular Attractions in 

 Solutions. 



The dimensions of a molecule of starch, according 

 to the estimate of Lobry de Bruyn, are of the order of 

 50 Angstrom units. Protein molecules containing 

 sulphur in the form of a cystine group, if that sulphur 

 amounts only to i per cent., as is commonly the case, 

 must have a molecular weight of not less than 6000 ; 

 and in the case of haemoglobin, as is familiar, the 

 percentage of iron points to a molecular weight nearly 

 three times this value. The dimensions of protein 



NO. 2683, VOL. 107] 



molecules are probably, therefore, of the same order 

 as those of the starch molecule. 



The radius of the sphere of molecular attractions is 

 also commonly estimated at 50 Angstrom units. This 

 means that in a solution of a substance the molecules 

 of which are of the size attributed to the molecules of 

 starch and many proteins, a molecule of the solute 

 will keep the molecules of the solvent on opposite 

 sides of it at such a distance from each other as to 

 be just out of range of each other's influence. The 

 molecules of the solvent at its surface must tend to 

 behave as if they were in a free surface of the solvent 

 faced by the solute — that is to say, they will be sub- 

 ject to internal pressure the resultant of which will 

 act in a line normal to the surface tending to draw 

 them away from it. Supposing that the molecules are 

 spherical, and that a sphere representing one of them 

 has as its diameter the radius SC (Fig. i) of the 

 sphere of molecular attraction about a molecule of 

 solvent at its surface at C : if a plane bisecting this 

 sphere of attraction be drawn tangential to the mole- 

 cule of solute through the line AB, which passes 

 through the molecule of solvent at the point C, then 

 the hemisphere ALB is the space within which other 

 molecules of solvent are all free to exert their attrac- 

 tion upon C, the resultant being a force acting in the 

 direction CL, as would be the case were it in a plane 



surface of the solvent. The other hemisphere ASB is 

 occupied as to one-quarter of its volume by the mole- 

 cule of solute, and the remaining three-quarters is 

 so disposed that the resultant of the attractions 

 exerted by the molecules of solvent in it which acts 

 in the direction CS is a fraction much smaller than 

 three-quarters of the opposite force acting in the direc- 

 tion CL, and therefore the sum of the two opposing 

 forces is a considerable force in the direction CL, 

 much greater than one-quarter of the internal pressure 

 of a molecule in a plane surface of the solvent ; in the 

 case of water, therefore, more than 2500 atmospheres. 



If the diameter of the molecule of solute were but 

 half that attributed to the molecule of starch, its 

 volume would be reduced to one-eighth of that in the 

 case presented in Fig. i, and the fraction of the hemi- 

 sphere ASB which it would occupy would be one- 

 thirty-second instead of one-quarter. The force acting 

 in the direction CS would be correspondingly increased, 

 and the resultant of this and its opponent would be a 

 force in the direction CL merely somewhat more than 

 one-thirty-second of the internal pressure on a mole- 

 cule in a plane surface. 



In the case of a molecule of the size attributed by 

 Nernst to a molecule of carbon dioxide, little more 

 than one-twentieth of that of a molecule of starch, 

 the fraction of the hemispherical space ASB which 

 it would occupy would be about 1/32000, and the 

 force tending to remove a molecule of solvent from 

 its surface would be about eight thousand times 

 smaller than that acting on solvent molecules in con- 

 tact with a molecule of starch, and something of the 

 order of 1/32000 of the internal pressure in a free 

 plane surface. 



