Dec. 2S, 1876] 



NATURE 



187 



-0040, -0'020, -o'ooi, -0040, -0004, -0-0I2, -0027, and 

 + 0*003 inch. Whether or not the readings in the paper be 

 reduced to sea-level, no information being given on this point, 

 the whole observations ot at least one of these two records are 

 entirely wrong. In explanation of discrepancies previously 

 pointed out, it was stated by the office that the original photo- 

 graphs may not admit of a precision closer than 0"020 inch. In 

 this case, however, such an explanation is out of the question. 

 Equally loose and inaccurate are the descriptions of the Kevv 

 curves, even though the main design of this costly system of 

 registration is to furnish data for exact comparisons being insti- 

 tuted among the different meteorological elements. Thus it is 

 stated that the electricity, having been strongly negative, re- 

 turned again to positive between 6 and 8 A. m., whereas the 

 change occurred all but instantaneously about 6.45 a.m. ; that 

 simultaneously with the time of maximum temperature, about 

 12.20 P.M., the wind, which had been west " suddenly became 

 north," whereas the change was not of such a character as to be 

 described by the words simultaneous and sudden, seeing that 

 about fifteen minutes elapsed as the wind veered from west to 

 north; that "the barometer rose rapidly until 4 P.M., at an average 

 rate of about 0005 per minute," whereas this rapid rate of in. 

 crease of pressure was spread over no more than the fifty minutes 

 from 2 to 2.50 P.M. It is needless to remark that the data of 

 this singular storm thus put before us are worse than useless 

 and it may be also state 1 that a number of the barometric ob- 

 servations at Kew, as published in the Hourly Readings for 

 March, are of such a character as to render a verification by 

 comparison with the originals very desirable. 



Diurnal Barometric Range at Low and High 

 Levels. — We have recently received trom Mr. W W. Rundell, 

 a paper on this important subject, published about two years ago 

 in the Jourttal of the Meteorological Society of London, based 

 on observations made under the direction of Gen. Myer during 

 May, 1872, on Mount W^ashington, New Hampshire, at heights 

 of 2,639 and 6,285 above the sea, hourly from 6 A.M. to 6 P.M., 

 and at 9 and 12 p.m., and at Portland, Maine, 54 feet above the 

 sea and near the coast, at 7 and 8 A.M., and at 2, 5, 9, and 

 12 P.M. The means of atmospheric pressure, temperature, and 

 humidity, are given for the different hours of observation, to 

 which are added interpolated values for the hours of the day for 

 which no observations were made, by drawuig a fair curve pass- 

 ing through the observed values plotted off on a moderately 

 large scale. These various averages are laid down in sets of 

 curves accompanying the paper. The point of interest raised by 

 suA a discussion consists in the presentation of these three vital 

 meteorological elements at three stations net far apart from each 

 other, but very differently situated as regards height above the 

 sea, and the probability that some light may thereby be thrown 

 on one of the most difficult problems in physics. On examining 

 the curves the attention is at once arrested by the remarkable 

 character of the curve of the diurnal barometric range at Port- 

 land, which represents the morning maximum as occurring at 

 6 AM., and the afternoon minimum at 2 P.M. Deductions of a 

 somewhat large nature are drawn from the times of occurrence 

 of these and others of the maxima and minima of the paper 

 tending to show that they stand to each other in certain definite 

 relations. Since, however, the facts of observation afford no 

 instance of the morning maximum occurring in May at such 

 places as Portland at 6 a.m., and the afternoon minimum at 

 2 p.m., we were led to calculate afresh the averages from 

 Gen. Myer's figures with the result that the averages of the six 

 hours of observations published in the paper are all in error in 

 amounts varying from + 0*027 inch to — 0-004 inch. The fresh 

 averages, it may be remarked, give an amplitude of range and 

 hours of occurrence of the extremes accordant with what has 

 beea observed in latitudes and situations similar to that of Port- 



land in May. It is obviously premature to discuss the various 

 points raised until the necessary data be put in order before us, 

 and the interpolated values for the unobserved hours be laid down 

 on a method based on a wide knowledge of observed values for 

 the same hours at places similarly circumstanced. 



The Climate ov Geneva. — A large work on this subject 

 has just been published by Prof. Plantamour, in which are dis- 

 cussed with clearness, precision, and great fulness, the observa- 

 tions made at the observatory during the past fifty years, on tem- 

 perature, pressure, moisture, rainfall, winds, clouds, and 

 thunderstorms. The hourly averages of the different elements 

 of each month for each year and for groups of years are given, 

 as well as the averages for each day of the year, and the average 

 or sums ot the pentades and months for the long periods 

 during which the observations have been made. There is 

 thus amasse-d in a handy form in one volume of 263 pp. 4to., 

 data for the elucidation of the climate of this part of Switzerland, 

 as well as for larger inquiries which fall to be dealt with by com- 

 parative meteorology, and for the investigation ot many cosmical 

 questions. Among the specialties of the climate of Geneva, the 

 most interesting, perhaps, are those which arise from its position 

 with reference to its lake. The variations in the direction and 

 force of the wind during the day show land and lake breezes of a 

 strongly marked character — the breeze from the lake prevailing 

 at those hours of the day when the temperature of the land is 

 in excess of that of the lake, and the land-breeze during the 

 rest of the day. In December, when the land at no hour 

 of the day is warmer than the lake, no breeze from the lake 

 prevails. In January, however, the breeze from the lake begins 

 slightly to prevail, and in an increasing degree in succeeding 

 months, forming a marked feature in the climate of the town 

 during the greater part of the year, and leaving iis im- 

 press in nearly all directions on the different meteorological 

 elements. During the winter months, when no breeze from the 

 lake prevails, or but a feeble one, the vapour curves show only 

 one daily minimum, occurring about sunrise, and one maximum 

 about 2 p.m. ; whereas during the other months, from March to 

 October, there occur two daily minima, one about or shortly 

 before sunrise, and the other from 2 to 4 p.m., and two maxima, 

 one from 8 to 11 A.M., and the other from 6 to 10 p.m., accord- 

 ing to season. Equally marked are the curves of the hourly 

 variations of cloud, the maximum during the winter months 

 occurring about sunrise and the minimum about sunset. During 

 the warm months, however, there are two daily maxima and 

 minima — the first maximum occurring about or shortly after sun- 

 rise, and the second, which is by far the larger of the two, about 

 6 P.M., and the two minima shortly after midnight and from 9 

 to II A.M. These variations in the moisture of the air of 

 Geneva are attributed by Plantamour to the condensation and 

 evaporation which take place at the surface of the earth, and to 

 the ascending and descending aerial currents consequent on the 

 diurnal march of the temperature. These are undoubtedly 

 true causes concerned in bringing about diurnal hygrometric 

 changes, but they are insufficient to explain the strongly-marked 

 double maxima and minima observed at Geneva. This will be 

 evident by a simple reference to the hygrometric curves for such 

 places as Valentia, Toronto, and Oxford, which either exhibit 

 no second maximum at all, or if they do, so faintly marked as 

 to form no outstanding feature of the curves. The explanation, 

 in all probability, of this peculiarity of the Geneva hygrometric 

 curves is to be found in the relative size of Lake Geneva 

 which is just large enough to occasion a strong breeze during the 

 day from the lake all round its shores. On the setting in of the 

 breeze, the air having been some time previously resting on the 

 surface of the lake is therefore moist, and while this continues 

 the first daily maximum is reached. As, however, the breeze 

 continues, the air feeding it must necessarily, owing to the cotti' 



