May 7, 1908] 



NA TURE 



The Warm Stratum in the Atmosphere. 



While not presuming to offer an explanation of the 

 isothermal or relatively warm stratum in the high atmo- 

 sphere, which the recent letters in Nature have made 

 known to others than meteorologists, I desire to point out 

 that it is probably a universal phenomenon, existing at 

 some height all around the globe. This inversion of 

 temperature was first discovered by M. Teisserenc de Bort 

 u-ith the baUoiis-sondes sent up from his observatory at 

 Trappes, near Paris, in 1901, and almost simultaneously 

 by Prof, .^ssmann from similar German observations. 

 .Since then almost all the balloons which have risen more 

 than 40,000 feet above Central Europe (that is, near lati- 

 tude 50°) have penetrated this stratum, without, however, 

 determining its upper limit. Teisserenc de Bort early 

 .-.bowed that its height above the earth, to the extent of 

 Sooo feet, varied directly with the barometric pressure at 

 the ground. Mr. Dines (N.\ture, p. 390) gives the average 

 height of the isothermal layer above England as 35,000 

 feet, with extremes of nearly 50 per cent, of the mean. 

 Observations conducted last March by our indefatigable 

 French colleague, Teisserenc de Bort, in Sweden, just 

 within the .Arctic circle, showed that the minimum tempera- 

 ture occurred at nearly the same height as at Trappes, 

 namelv, 36,000 feet, although Prof. Hergesell, who made 

 Use of baUoiis-soiidcs over the -Arctic Ocean, near latitude 

 75° N., during the summer of 1906, concluded that the 

 isothermal stratum there sank as low as 23,000 feet. 



During the past three years the writer has dispatched 

 seventy-seven ballons-sondes from St. Louis, U.S. .A., lati- 

 tude 38° N., and most of those which rose higher than 

 43,000 feet entered the inverted stratum of temperature. 

 This was found to be somewhat lower in summer, but the 

 following marked inversions were noted last autumn : — 

 October S, the minimum temperature of —90° F. occurred 

 at 47,600 feet, whereas at the maximum altitude of 54,100 

 feet the temperature had risen to —72°; October 10, the 

 lowest temperature of —80° was found at 39,700 feet, 

 while —69° was recorded at 42,200 feet, showing a descent 

 of nearly Sooo feet in the temperature-inversion WMthin 

 two days. The e.xpedition sent out jointly by M. 

 Teisserenc de Bort and the writer, on the former's steam 

 vacht Otaria, to s6und the atmosphere over the tropical 

 .Atlantic during the summer of 1906, launched ballons- 

 sondes both north and south of the equator within the 

 tropics, and although some of these balloons rose to nearly 

 50,000 feet, thev gave no indication of an isothermal 

 stratum. In fact, the paradoxical fact was established 

 that in summer it is colder eight miles above the thennal 

 equator than it is in winter at the same height in north 

 temperate regions. This results from the more rapid de- 

 crease of temperature in the tropics and the absence of the 

 numerous temporary inversions which, as Mr. Dines has 

 pointed out, are common in our regions below 10,000 feet. 

 If. therefore, as seems probable, the isothermal or 

 relatively warm stratum does exist in the tropical and 

 equatorial regions, it must lie at a height exceeding 

 50.000 feet, from which height, as the data quoted show, it 

 gradually descends towards the Pole, at least in the 

 northern hemisphere. 



A. LAWRENCE ROTCII. 



Blue Hill Meteorological Observatory, Hyde Park, 

 Mass., U.S. .A., April 24. 



The Nature of X-Rays. 



Prof. Br.\gg in a recent letter (X.xture, .April 16) credits 

 me with the admission that the experiments I inade on 

 the intensitv of secondary (scattered) X-rays are not so 

 contrary to the neutral pair theory as I at first supposed. 

 Will you permit me to correct this by saying that all the 

 evidence I have obtained has verified the ether pulse theory 

 in a more striking way than I ever anticipated, and I 

 lannot think of a single experimental result obtained in 

 researches on secondarv X-rays which gives any support 

 to his theory ? 



Prof. Bragg refuses, on the plea of want of Icnowledge 

 of the constitution of the atom, to accept as conclusive 



N"0. 2010, VOL. 75] 



the results of experiments I recently made. It appears to 

 me, however, that such absence of knowledge is insufficient 

 to conceal the disproof of his theory, and that the evidence 

 (though by itself not sufficient to establish any theory) is 

 quite sutlicient to distinguish between the ether pulse theory 

 and that proposed by Prof. Bragg. 



The supposed difficulty in accounting on the ether pulse 

 theory for the change in the ratio of intensities, to which 

 he refers, is not one affecting the theory at all. Sufficient 

 experiments have not yet been made to lead to a final 

 choice between several possible causes as producing the 

 bulk of this effect. The result itself is in harmony with 

 the results of other experiments. 



.As Prof. Bragg is apparently not convinced, I venture 

 to recommend the consideration of the following evidence 

 obtained in investigating secondary X-rays, for I can only 

 think that the study of this evidence would at least lead 

 him to confine the application of his hypothesis to the 

 explanation of phenomena which at any rate do not furnish 

 so striking a disproof. 



The evidence may be briefly summarised as follows : — • 



(i) The partial polarisation of a primary beam of X-rays. 



(2) The identity in penetrating power of secondary 

 (scattered) rays from light atoms, and of the primary pro- 

 ducing them, though the scattered constitute only a fraction 

 of the incident rays. 



(3) The equality in the proportion of rays of different 

 penetrating power which are scattered. 



(4) The fairly complete polarisation of the rays scattered 

 in a direction perpendicular to that of propagation of the 

 primary. 



(5) The distribution of the secondary (scattered) rays. 



(6) The order of magnitude of the energy of scattered 

 radiation. 



(7) The homogeneity of a second type of secondary 

 X-radiation from many substances. 



(8) The fact of this homogeneous radiation being 

 characteristic of the element emitting it, and independent 

 of the penetrating power of the primary radiation pro- 

 ducing it. 



(9) The fact that for large ranges in the penetrating 

 power of the primary these homogeneous secondary rays 

 from some substances are proportional to the ionisation 

 produced by the complex primary in air. 



These are points that occur to me while writing; there 

 are probably others. 



The first five results (though not explicitly stated) were 

 contained in the theory as given by Prof. J. J. Thomson 

 (" Conduction of Electricity through Gases ") shortly after 

 the publication of the second experimental result, and 

 before the others were experimentally observed. The sixth 

 is in harmony with the calculation given by Prof. Thomson 

 if we accept his theory of the number of electrons in the 

 atom. Results (7), (8), and (9), obtained in joint-work 

 with Mr. C. A. Sadler, can be explained on the ether pulse 

 theory. 



Prof. Bragg has given an explanation (based on what 

 seem to me doubtful assumptions as to the behaviour of 

 a neutral pair on collision with light atoms) of the fourth 

 result. An explanation on his theory of the other facts 

 necessitates in some cases very improbable, assumptions; 

 in others it appears to me to lead to absolute impossibili- 

 ties. In no case can I find the slightest support for the 

 neutral pair theory. 



Regarding the nature of 7 rays, or even of very pene- 

 trating X-ravs, the direct evidence is much less conclusive, 

 the corresponding phenomena being in reality more 'com- 

 plex, for reasons which are beginning to be understood. 

 For that reason I do not wish at present to discuss them, 

 preferring to deal with what is to me a certainty, and 

 waiting for the results of further experimental w-ork to 

 throw light on the more complex. Prof. Bragg commences 

 at the other end with a hypothesis which gives an easy 

 explanation of what on the pulse theory is somewhat 

 obscure, but when an attempt' is made to apply this to 

 the simpler phenomena it is found inadequate, not only 

 as a complete theory, but even as a supplementarv one. 



CH.^RLES G. B.4RKLA. 



Liverpool, .April 27. 



