26o 



NATURE 



[October 20, 192 1 



instead of one big quantum ; this in turn seriously 

 affects the logic of the deduction of the energy of 



activation from the temperature coefficient of the 

 reaction. 



_ Again, we may assume that when there is a con- 

 tinuous drain on one portion of the spectrum by ab- . 

 sorption of the light of one particular frequency, the I 

 rest of the spectrum undergoes a continuous redis- | 

 tribution of the energy involving an increase in the 

 absorbed radiation density and a decrease in the 

 density of the radiation of greater and smaller wave- I 

 length. To account for such an hypothesis we must 

 assume that there is some mechanism for the absorp- i 

 tion of these rays in order to effect the redistribution, 

 the purely monochromatic character of the reaction i 

 being thus lost, and a parallelism between these 

 thermo- and photo-chemical reactions no longer 

 exists. It is, of course, evident that such a 

 redistribution of the energy does not take place 

 when a reaction is illumined with ordinary visible i 

 light, since definite absorption bands are noted, 

 and the rest of the energy either passes through i 

 the reaction chamber or is scattered from the 

 molecule surfaces. A third hypothesis involves ; 

 the assumption that the radiation' density inside the | 

 actual molecules themselves is the important factor, i 

 and one which is greatly influenced by the refractive ' 

 index of the molecule ; computations on these lines 

 lead to high values for the refractive index of the 

 region inside the molecules which await other inde- 

 pendent confirmation. 



A second difficulty has been raised by a study of 

 hydrolytic operations, e.g. sucrose; the temperature 

 coefficient of the reaction indicates an activating fre- 

 quency in the infra-red portion of the spectrum. 

 Illumination with bright sunlight should cause a very 

 great increase in the reaction velocity ; no perceptible 

 effect is actually observed. It is, however, possible 

 to attribute the comparative inertness of these re- 

 actions to the strongly absorbent character of the 

 environment to light of long wave length ; and it has 

 been suggested that a study of the reaction velocity 

 in thin films under illumination might lead to positive 

 results. 



Of significance is the fact that the substance for 

 which the activating frequency has been calculated 

 from the temperature coefficient frequentlv shows no 

 absorption band in that region. If the hypothesis be 

 adopted that the activating frequency calculated in 

 this manner is only a mean value, i.e. the possibility 

 of activation in stages be envisaged, we are con- 

 fronted with a difficulty in calculating the reverse 

 operation, viz. the reaction velocity from a know- 

 ledge of the complete spectrum of the reacting system, 

 since we have no information as to the manner of 

 the distribution of the partially activated molecules. 



The debate served clearly to emphasise the relation- 

 ship of the quantum hypothesis to chemical action, and 

 the fact that the radiation theory was not entirely 

 convincing, but, on the other hand, it certainly con- 

 tains the germ of the solution to the problem of the 

 mechanism of the interaction of matter and radiation. 



The Teaching of Geography. 



T N opening the discussion on the teaching of 

 ■*■ geography at a joint meeting of the Sections of 

 Geography and Education of the British Association 

 at Edinburgh on September 9, Mr. G. G. Chisholm 

 laid stress on the physical basis of geography, but 

 urged the importance of regarding the physical 

 agencies not so much as changing the face of Nature 

 as influencing the distribution of man and his activi- 

 ties. Mr. Chisholm pointed out that geographers have 

 now reached a considerable measure of agreement in 

 the work included under the head of geography. That 

 agreement marks a step in the better recognition of 

 geography in the educational curriculum. At a later 

 stage in the discussion Dr. H. R. Mill dwelt on the 

 urgent necessity of quantitative work in geographical 

 research, and pointed out the enormous field of study 

 which this opens. 



Sir Richard Gregory spoke of the position of geo- 

 graphy in relation to other science subjects in the 

 school curriculum. He advocated a course of general 

 science as more useful for a general education than 

 the beginnings of heat and light and the laws of 

 chemical action for pupils up to the age of sixteen. 

 A course in geography for all pupils up to that age 

 would at the same time provide the unifying principle 

 for all the science work, bringing it into relation with 

 the activities of man. After such a course it would 

 be equally easy for pupils to specialise in mathe- 

 matics, physics, chemistry, or geography. At present 

 there tends to be a gap in geographical teaching 

 between school and university work, because few 

 schools have geography teachers capable of carrying 

 the subject to a standard equivalent with the teaching 

 in chemistry and physics. 



Mr. W. H. Barker deprecated the tendency to divide 

 studies into watertight compartments, and insisted 

 that the teaching in geography must be given, not by 

 the science master, but by a geography specialist who 

 by his training is fitted to bring out the unifying 

 NO. 2712, VOL. 108] 



influence of the subject. Geography serves to unite 

 the two main groups of subjects, natural sciences and 

 humanities, and therein lies its great educational 

 value. To reunite the specialisations is the function 

 of the geography teacher. 



Some of the difficulties of getting adequate recogni- 

 tion of geography in the university curriculum were 

 pointed out by Dr. Rudmose Brown. The rigid divi- 

 sion of studies into the faculties of arts and science 

 is only slowly breaking down, and, in consequence, 

 geography has a fight to find its true position. The 

 geographer has a definite outlook, and his subject is 

 the same, no matter in which faculty it is placed. 

 The narrow conception of science as being confined 

 to the so-called natural sciences must give way before 

 geography can find adequate recognition. Meanwhile, 

 the practical result of dividing knowledge by a rigid 

 line of demarcation is reflected in the difficult task 

 of giving students of geography the wide outlook 

 that the subject requires. 



A plea for the value of geography in historical study 

 was made by Prof. R. K. Hannay. He complained 

 of the non-geographical attitude of many historians, 

 and urged that students of history should follow 1 

 courses in geography. Prof. J. W. Gregory, in ent^ 

 phasising the scientific basis of geography, though^ 

 that it should be included in the science faculties of 

 universities, but did not disparage its inclusion amonj 

 arts subjects. \\'hile there has been much improve* 

 ment.in geographical education in Scotland in recent 

 years, the subject still suffers from neglect and failur 

 to take its due portion in education. This is most 

 noteworthy in secondary schools. Dr. F. Mort was 

 hopeful of the position of geography in Scottisl 

 schools, and quoted figures to show the increase 

 numbers taking advanced work in the subject ant 

 taught by specially trained teachers. Prof. J. A; 

 Green regretted that much school geography was 

 above the heads of the pupils, the teacher not vkA 



