August 15, 1901] 



NA TURE 



Zll 



flower should be fertilised by pollen from the wild fig, or 

 caprifig. The pollen is conveyed by an insect, Blasto- 

 p/iaga grossorum, which goes through its various stages 

 of growth in the wild fig. It is the practice in Smyrna 

 and other fig-growing countries to break off the fruits of 

 the caprifig, and tie them to the limbs of the edible fig 

 tree, at the time when the flower receptacles of the 

 latter are in a suitable condition. The result is the pro- 

 duction of figs far larger and finer than would be 

 obtained without this operation. The American report 

 gives a brief history of our knowledge on this subject, 

 and a detailed account of the introduction of the Smyrna 

 fig into California, the subsequent introduction of the 

 caprifig, and the final successful introduction, after 

 several failures of the insect, with details of the work 

 done during the season of 1S99, when the first crop of 

 figs fully equal to the imported article was obtained. 

 For the successful fertilisation of the Smyrna fig it is 

 necessary that the caprifig should blossom at the same 

 time as the Smyrna fig, and that the winged female 

 insect should also at the same time be emerging from 

 the galls containing the pupa. These adjustments are 

 liable to be disturbed by variations in climate and 

 season, and require careful study and skilled scientific 

 superintendence if fig culture is to be successfully 

 introduced into a new country. 



The report on the cultivation of the date palm is also 

 of great interest. A full account is given of the con- 

 ditions under which the finest dates are produced in 

 Algeria and the Sahara, and of the steps which have been 

 taken to introduce the best varieties of the date palm into 

 Arizona and other suitable climates in the United States. 

 It is shown that the best varieties can only be introduced 

 by means of offshoots, the plants grown from seed 

 being very various in character. Different climates re- 

 quire the choice of different varieties. The tree has the 

 great merit of flourishing in climates in which the 

 summer is too hot and too dry to permit of ordinary 

 cultivation ; it flourishes even in soils impregnated with 

 alkali salts, a condition frequently met with in dry 

 climates. The report should be of considerable value to 

 the Agricultural Department of our Indian Empire, where 

 vast areas of waste alkali land are still waiting to be 

 dealt with. 



There is one more report, of special interest in con- 

 nection with the present summer, of which we will briefly 

 speak : its subject is hot waves, the conditions which pro- 

 duce them and their effect on agriculture. The continent 

 of North America is at present admirably suited for the 

 study of meteorological phenomena ; the observers 

 cover an immense area, and are all in telegraphic com- 

 munication with the Central Weather Bureau at Wash- 

 ington. The report in question includes the study of 

 three remarkable periods of heat, and is illustrated by 

 maps showing the distribution of pressure and temperature 

 over the continent during these periods. The first point 

 that strikes one is the unsuitableness of the phrase " hot 

 wave." The heat periods are, indeed, periods of stagna- 

 tion in the atmosphere. The conditions appear to be 

 similar in each instance which is discussed. There is an 

 area of moderately high pressure in the subtropical region 

 towards the south-east ; an area of moderately low 

 pressure in the northern central States, and a second 

 NO. 1659, VOL. 64] 



area of high pressure on the west or north-west coast. 

 These conditions aie steadily maintained during the hot 

 period. There is, of course, a slow flow of air from the 

 subtropical, south-eastern area of high pressure to the 

 central or north-central area of low pressure. The extreme 

 temperatures occur between these two regions. The 

 great heat is not simply due to air coming from a warm 

 region ; it is largely due to the clear sky affording full 

 opportunity for the receipt of solar energy, and to the 

 small radiation during the night from the earth's surface ; 

 the hot nights are, indeed, a striking feature of these 

 periods. What is the cause of this absence of night 

 radiation with an apparently clear sky? It appears to be 

 due to the presence of a large quantity of transparent 

 water vapour in the higher regions of the atmosphere, 

 which allows the passage of solar radiation but forbids 

 the return of the lower grade heat waves of terrestrial 

 radiation. R. Warington. 



SCHOOL HYGIENE. 

 School Hygiene. By Edward Shaw, Professor 01 the 

 Institutes of Pedagogy, New York University. Pp. 260. 

 (London : Macmillan and Co., Ltd., 1901.) 4J. bd. net. 



A Manual of School Hygiene. By E. W. Hope, jM.D. , 

 Professor of Hygiene, University College, Liverpool, 

 and E. A. Browne, F.R.C.S.E., Lecturer of Ophthal- 

 mology, University College, Liverpool. Pp. 207. (Cam- 

 bridge : University Press, 1901.) 3^-. 6rf. net. 

 IT has been the aim of the authors of these two works 

 to set forth the conditions which should surround 

 school pupils in order that their mental and physical 

 health may be promoted. No true education in mental 

 training can overlook the hygienic and physical relation- 

 ship of mind and body, and no knowledge must be 

 conveyed at the expense of physical and moral develop- 

 ment ; for it is true, as Mr. Herbert Spencer has 

 reminded us, that the essential object of education is to 

 teach us how to live happily. Moreover, the connection 

 between physical health and the power of voluntary 

 control and, consequently, of conduct, is very close, and 

 perfect mental development cannot be brought about if 

 the opportunity is not given for healthy physical de- 

 velopment. Notwithstanding the general acceptance of 

 these truisms, school buildings are still being erected 

 with a view mainly to e.Kterior effect, and an adequate 

 system of ventilation in the crowded class-rooms is 

 rarely to be met with. .As Prof Shaw has pointed out, 

 the school-room should be the unit first to be considered 

 in planning the school buildnig, and the building should 

 be a number of school-rooms properly disposed, and not 

 a whole cut up into school-rooms whose size and arrang e- 

 ment are dependent upon the size and shape of the 

 building. 



The guiding principles of hygiene, so far as it is 

 affected by the circumstances of school life, are well and 

 clearly set forth in both books, and the essential facts of 

 school health are brought within the easy reach of the 

 parent or teacher. To do their duty in this respect, no 

 great amount of detail knowledge is necessary, but 

 rather one of general principles combined with an intel- 

 ligent observation of children with the view of detecting 



