Jtme 30, 1887] 



NATURE 



195 



With eighteen years' observations (1866-83) at Ivigtut, 

 Godthaab, and Jacobshavn, and nine years' (1875-83) at 

 Upernivik, we can now present, with an approximate 

 correctness not hitherto attainable, the distribution of 

 pressure over Greenland during the months of the year. 

 The following mean pressures, at 32° and sea-level, give 

 the highest and lowest, with the months of their 

 occurrence : — 



Year. 

 Inches. 



29 666 

 •684 

 749 



753 



Thus in Greenland pressure increases with latitude. 

 The difference between the extreme south and north is in 

 January 0*205 inch, and in spring 0*154 inch ; but the dif- 

 ference in summer is small, being in July only 0008 inch. 

 The above mean of January- at Ivigtut 29*398 inches, and 

 for the same month at Stykkisholm in the north-west of 

 Iceland 29*396 inches, are, so far as known, the lowest 

 mean monthly pressures anywhere yet observed in the 

 northern hemisphere ; and it is interesting to note that it 

 is in the region immediately to the south and south-west of 

 these places that a very large number of our European 

 storms have their origin. 



Attention is forcibly drawn by the 186 charts of pres- 

 sure and wind to the remarkable fact that the depression 

 areas of Greenland appear to travel from north to south. 

 An extension of the area charted would doubtless show 

 that while in many cases these areas travel northwards 

 yet in a considerable number of cases this direction is 

 more apparent than real. It is, however, abundantly 

 evident that Greenland exerts an important influence on 

 our Atlantic storms that remains still to be investigated. 



The most elaborate part of the paper is the discussion 

 of the diurnal curves of pressure from the hourly observa- 

 tions. The curve for the year exhibits the two usual 

 maxima at 8 a.m. and 8 p.m., and the two minima at 

 2 a.m. and i p.m., the morning minimum and the evening 

 maximum being respectively the greater, and these fea- 

 tures of the curves are, with one exception, reproduced in 

 the curves for the months. The results will be made to 

 tell their story more clearly if we eliminate the more 

 prominent irregularities attaching to means of one year 

 only, by blo.vaming the hourly means, by taking for the 

 hourly means of each month means calculated from that 

 month, the month immediately preceding, and that imme- 

 diately following it. In ^these new mean hourly values 

 the morning greatly exceeds the evening maximum in 

 February, March, and April, whereas in every other 

 month the reverse holds good, and that in a very pro- 

 nounced degree. On the other hand, the morning greatly 

 exceeds the afternoon minimum in each month of the 

 year. From the relations the results show to those 

 for places in similar situations in lower latitudes, we may 

 conclude that unusual care has been taken in securing for 

 the barometer a position where it was subject to only a 

 very small daily change of temperature. It is absolutely 

 necessary that this condition should be attended to, if 

 observations arc to be of any use at all in the discussion 

 of the important question of the horary variations of 

 pressure in high latitudes. Since the variations dealt with 



seldom exceed o*oio inch, and are generally much less, it 

 is evident that the inquiry is for these regions a refined 

 one ; hence it is essential that the attached thermometer 

 should represent the temperature of the whole instrument 

 to within 1° F. It is the neglect of this point that vitiates 

 several series of horary barometric observations in the 

 Arctic regions. 



Over the open sea in high latitudes during the summer 

 months, where the sun either does not set, or only for a 

 brief interval, the diurnal curve of pressure diffiers essen- 

 tially from the above. The observations made by the 

 Challenger Expedition in the Antarctic Ocean, and those 

 made by the Norwegian Expedition in the north of the 

 Atlantic, show only one maximum and one minimum in 

 the day, the maximum occurring during the day and the 

 minimum during the night. This peculiar curve is re- 

 stricted to the open sea of high latitudes. Director 

 Paulsen is inclined to the opinion that the diurnal varia- 

 tion of pressure at Godthaab is caused not so much by 

 local variations of temperature and humidity as by trans- 

 missions from lower latitudes of their diurnal variations of 

 pressure. In this opinion we to some extent concur, it 

 being probable that some of the more prominent features 

 of these daily curves of pressure are the results of vast 

 quasi-tidal movements communicated through the higher 

 regions of the atmosphere, in which the space traversed 

 by the individual aerial molecules is not necessarily great. 



OUR BOOK SHELF. 



Essays and Addresses. By the Rev. James M. Wilson, 

 M.A. (London : Macmillan and Co., 1887.) 



In these "Essays and Addresses" Mr. Wilson deals 

 chiefly with problems connected with religion and 

 morality, and his main object seems to be to show that 

 theological and ethical principles, properly interpreted, 

 are supported, instead of being contradicted, by scientific 

 ideas. The book is evidently the result of much inde- 

 pendent reflection. Mr. Wilson tries to grapple with no 

 intellectual difficulty which he has not thoroughly 

 examined, and in all his statements of scientific doctrine 

 he is scrupulously exact. He refers to science in so 

 many aspects that much of what he has to say may be 

 studied with interest even by readers who do not feel that 

 his arguments with regard to such subjects as " Miracles'' 

 and " Christian Evidences " are perfectly conclusive. 



Introductory Text-book of Physical Geography. By the 

 late David Page, LL.D., F.G.S. Twelfth Edition. 

 (Edinburgh and London : W. Blackwood and Sons, 

 1887.) 

 This book was originally published about twenty-five 

 years ago, and has done good service in many schools 

 and colleges. After the author's death it was brought up 

 to date by Dr. Charles Lapworth, who, besides making 

 a number of minor corrections and additions, contributed 

 a summary of those results of the Challenger Expedition 

 which had reference to the depths, deposits, and tem- 

 perature of the ocean ; an account of British storms ; a 

 description of the biological regions of the earth ; and a 

 short sketch of Prof. Huxley's arrangement of the human 

 family. In the present edition Dr. Lapworth has again 

 sought to bring the work abreast of scientific know- 

 ledge, introducing new matter relating to geology and 

 petrography, meteorology and climatology, and the dis- 

 tribution of animals and plants. On the latter subject he 

 has obtained from Prof. D'Arcy Thompson an excellent 

 summary of recent biological research and theory. The 



