November 17, 192 1] 



NATURE 



2>77 



dearly that he who runs may read their substantial 

 identity. The actual gap in the spectrum of the 

 known radiations between light and X-rays is also 

 rapidly disappearing. The longest stride into the 

 region beyond the ultra-violet was made by Lyman 

 with the vacuum grating spectroscope which he 

 developed. For a time Prof. Bazzoni and I held 

 the record in this direction with our determination 

 of the short wave limit of the helium spectrum, 

 which is in the neighbourhood of 450 Angstrom 

 units. More recently this has been passed by 

 Millikan, who has mapped a number of lines ex- 

 tending to about 200 ngstrom units — that is to 

 say, more than four octaves above the violet limit 

 of the visible spectrum. I am not sure w'hat is 

 the longest X-ray which has been measured, but 

 I find a record of a Zinc L-ray by Friman [Phil. 

 Mag., vol. 32, p. 494, 1916) of a wave-length 

 of 12-346 Angstrom units. There is thus at most 

 a matter of about four octaves still to be explored. 

 In approaching this unknown region from the 

 violet end the most characteristic property of the 

 radiations appears to be their intense absorption 

 by practically every kind of matter. This result 



is not very surprising from the quantum point of 

 view. The quantum of these radiations is in 

 excess of that which corresponds to the ionising 

 potential of every known molecule, but it is of the 

 same order of magnitude. Furthermore, it is 

 large enough to reach not only the most super- 

 ficial, but also a number of the deeper-seated elec- 

 trons of the atoms. There is evidence, both 

 theoretical and experimental, that the photo-elec- 

 tric absorption of radiation is most intense when 

 its quantum exceeds the minimum quantum neces- 

 sary to eject the absorbing electron but does not 

 exceed it too much. In the simplest theoretical 

 case the absorption is zero for radiations the fre- 

 quencies of which lie below the minimum quan- 

 tum, rises to a maximum for a frequency com- 

 parable with the minimum, and falls off to zero 

 again at infinite frequency. This case has not 

 been realised in practice, but, broadly judged, the 

 experimental data are in harmony with it. On 

 these general grounds we should expect intense 

 absorption by all kinds of matter for the 

 radiation between the ultra-violet and the X-ray 

 region. 



The Botanic Gardens, Victoria, Cameroons Province, Nigeria. 



Nigeria, 



in a 



Council,^ 



by those 



colonies, 

 condition 



in the 



HIS Excellency the Governor of 

 Sir Hugh Cliflford, G.C.M.G. 

 remarkable address to the Nigerian 

 which is deserving of careful study 

 interested in our West African 

 directed attention to the neglected 

 of the \'ictoria Botanic Gardens 

 recently acquired Cameroon Province, and stated 

 that at his request the Assistant Director of the 

 Royal Botanic Gardens, Kew, was about to visit 

 Nigeria for the purpose of advising the Govern- 

 ment "as to the action that should be taken for 

 their restoration and future maintenance." We 

 learn from the iveic Bulletin, No. 6, issued in 

 September last, that Captain A. W. Hill has re- 

 turned from his mission, and fully endorses the 

 remarks made by the Governor as to the beauty 

 and value of these gardens. 



To quote from His Excellency's address : — 



The Botanical Gardens at Victoria compare in 

 everything save size with their prototypes at Buiten- 

 zorg in Java and Peradeniya in Ceylon. They con- 

 tain a fine and varied collection of trees and plants and 

 shrubs which have been brought together from every 

 part of the tropics; and, in spite of their close 

 proximity to the sea, the soil in them appears to be 

 abundantly fertile. A special feature of these gardens 

 is a stream of water, crystal clear, that patters noisily 

 over a bed of pebbles. ... 



It would be a lasting discredit to this Government, 

 I consider, if it were to neglect to repair the damage 

 which the war has already unhappily inflicted upon 

 these lovely and valuable gardens. 



The gardens, we learn, cover an area of some j 

 200 acres, and are provided with a good labora- , 



1 Nigerian Council, Address by the Governor, Sir Hugh Clifford' I 

 December 29, 1920. See especially pp. 184-86 and 208-11. i 



NO. 2716, VOL. 108] 



tory, a herbarium, and museum building, as well 

 as a building which served the purpose of an 

 agricultural school. All these are in a very fair 

 state of repair, and are only awaiting the time 

 when they can be restored to their proper func- 

 tions. The site is admirably adapted to garden 

 purposes, since the soil is a highly fertile decom- 

 posed volcanic rock. There are some steep hills, 

 commanding fine views either across the bay or 

 to the lofty Cameroon Mountain, but there is also 

 a considerable tract of more or less level ground, 

 so that it is possible to cultivate useful economic 

 plants under varied tropical conditions. Con- 

 nected with these gardens were the experimental 

 plots of tea and cinchona at Buea, situated at an 

 altitude of 3300-3600 ft., on the slope of the 

 Cameroon Mountain. Photographs of these 

 plantations are given in the Bulletin, and though 

 now in a very neglected condition, they show that 

 the cultivation of these products is a practical 

 proposition in the Cameroon Province. High- 

 level stations are thus a necessary adjunct to the 

 gardens. 



The importance of the Victoria Botanic 

 Gardens and substations, with the laboratory and 

 other buildings, where mycological, chemical and 

 entomological research can be carried out, can 

 best be realised when it is pointed out that the 

 lower slopes of the Cameroon Mountain are 

 covered by extensive plantations of such economic 

 plants as cocoa, coffee, Hevea and Funtumia 

 rubber, kola, bananas, oil palms, etc. The 

 Cameroon Province thus differs essentially from 

 Nigeria proper, where large plantations are rare 

 and widely separated. In Nigeria fungus and 

 insect diseases are not able to spread far, since 



