242 SCIENCE. 



new Botanical Institute built and presented to the University Of 

 Genoa by the munificence of Mr. Thomas Hanbury, of La Mor- 

 tola, and the opening of an Exhibition of Horticulture. All com- 

 munications should be addressed to Professor Penzig of the 

 University of Genoa. 



—In the Annual Report for 1892 of the Berlin branch of the 

 German Meteorological Society, Professor G. Hellmann gives an 

 account of his continued experiments, which are summarized in 

 Nature, on the eflFects of exposure on rainfall records, and on the 

 determination of the distance apart that rain-gauges should be 

 erected in order to obtain an accurate account of the rainfall of 

 any district. Simple as the question appears, the experiments, 

 which have been carried on for seven years, have not sufficed to 

 give a definite answer. Very considerable differences are found 

 in the amounts recorded at stations comparatively close to each 

 other. This result is partly owing to the effect of wind, especially 

 in the case of snow. The following are the most important con- 

 clusions derived from the experiments: (1) The more a rain- 

 gauge is exposed to the wind, under otherwise similar circum- 

 stances, the less rainfall it records, and the higher a gauge is 

 placed above the ground, the less rain it catches, as the disturb- 

 ing influence of the wind is greater than on the surface of the 

 ground. But if protected from the wind, a gauge will give use- 

 ful results in an elevated position. The usual instructions to 

 erect the gauge as openly as possible are therefore incorrect. (2) 

 Even in a flat country, differences of 5 per cent occur in different 

 months, at stations a quarter of a mile apart ; in stormy weather, 

 especially during thunderstorms, the difference may amount to 

 100 per cent. The amounts recorded at neighboring stations 

 agree better together in spring and autumn, and also in relatively 

 wet years. Further experiments are needed, if possible by means 

 of anemometers erected at the same level as the rain-gauges, to 

 determine more accurately the effect of wind on both rainfall and 

 snow. 



— At a meeting of the Engineers' Club of Philadelphia, April 2, 

 Mr. W. S. Auchincloss read a paper on Yearly Tides. In this 

 paper the author stated that he proposed to show that confined 

 bodies of fresh water are subject to yearly tides of greater or less 

 magnitude, depending upon the nature of the basin or upon the 

 strata to which they are confined, and upon the effect of evap- 

 oration if in an open basin. In March, 1885, he had occasion to 

 sink a well near Bryn Mawr, Pa. Natural anxiety as to the per- 

 manence of the supply led him to observe the depth of the water 

 at intervals of about ten days. It soon became evident that the 

 water was receding. In 1886 there was a gratifying rise of the 

 surface and a total gain of 12 feet. His curiosity was aroused 

 and he determined to study the law, if such a law existed, of 

 this ebb and flow. These observations have been continued dur- 

 ing the past seven years. He found that in normal years the 

 surface of the water reaches its lowest level in December, rises 

 until June, and descends during the autumn. An examination 

 of the amount of the rainfall shows that while the amount of 

 rainfall was as great or greater during the last half of the year as 

 during the first, the level of the water in the well continually 

 lowered. Atmospheric temperature had practically no effect, 

 as the temperature of the water in the well is practically constant 

 all the year round. The depth of the well prevented evaporation 

 from its surface from having any effect. The author believes 

 that the true cause is the result of the influences of gravity and 

 of the sun's attraction at different seasons of the year. When 

 the sun reaches its furthest point south of the equator, gravity 

 exerts its maximum influence on the waters pt the northern 

 hemisphere. The waters of the earth will be drawn into the 

 minutest crevices and the surfaces lowered, but in June they will, 

 in a measure, be released, and, under the influence of adhesion 

 and friction, will be held at a higher level than during any other 

 season of the year. Data obtained from the Government records, 

 showing the depth of water in the Great Lakes, show that 

 there is a similar rise and fall, the range of yearly ebb and flow 

 being from 12 to 15 inches in our northern lakes. So far as we 

 are aware, no data exist for the small lakes. More extended re- 

 search will, we believe, secure as complete a recognition of yearly 



[Vol. XIX. No. 482 



tides as physical geography has always accorded to the phenom- 

 enon of daily tides. The author presented two diagrams, one of 

 which showed the rise and fall of the water in the well covering 

 a period of seven years, and also the northing and southing of the 

 sun for the same period. 



— In February, 1890, a grant was made by the Royal Society 

 for the purpose of supplying the Ben Nevis Observatory with 

 apparatus for counting the number of dust-particles in the air. 

 Two instruments, one portable and another of larger dimensions, 

 were made after designs by Mr. Aitken. With the latter observa- 

 tions may be made at any time, except when the wind, blowing 

 from the south-west, pollutes the air above the inlet pipes with 

 smoke from the observatory and hotel. Since February, 1891, 

 observations have been made every third hour. Some of the re- 

 sults are given, and their bearing discussed, by Mr. Angus Rankin 

 in the Journal of the Scottish Meteor. Soc, Third Series, No. viii. 

 It may be stated that a number of particles under 100 in a cubic 

 centimeter of air is phenomenally small, and a number over 4,000 

 phenomenally large. The highest number was 14,400, which was- 

 counted in April, 1891. The particles are most numerous during 

 March, April and May, when easterly and south-easterly winds 

 are prevalent both at sea-level and on the summit of the moun- 

 tain. On the other hand, when the winds on Ben Nevis blow 

 from the north-west, north, or east, their directions diverge most 

 from those of sea-level winds, and then the dust-pai tides are 

 most scarce. Hourly observations were made only on four days, 

 but the three-hourly means show the general trend of the daily 

 curve. The means for the three months, March to May, show a 

 minimum, 526, at 4 hours, and a maximum, 1,438, at 16 hours, 

 the absolute mean for the three months being 854. The varia- 

 tions seem to be due to the movements of the first, or lowest, 

 cloud stratum. In the morning this stratum lies below the sum- 

 mit of Ben Nevis, but towards noon rises and envelopes the top, 

 hovers above it in the afternoon, and sinks to its original position 

 about midnight. Several points remain to be cleared up. Ap- 

 parently only the free dust-particles are counted, and few, if any, 

 of those on which moisture has condensed to form visible fog; 

 all the lowest values have been recorded when a thin mist envel- 

 oped the top. These observations will be of great service in the 

 study of clouds — their forms, heights, and motions. The bearing 

 of dust on the humidity of the air is also an important point; at 

 present the humidity of the Ben Nevis atmosphere is very little 

 understood. 



— The papers entered to be read at the April meeting of the 

 National Academy of Sciences were as follows: An American 

 Maar, by G. K. Gilbert ; The Form and Efficiency of the Iced Bar 

 Base Apparatus of the United States Coast and Geodetic Survey, 

 by R. S. Woodward (introduced by T. C. Mendenhall) ; On Atmos- 

 pheric Radiation of Heat in Meteorology, by C. Abbe; On the De- 

 flecting Forces that Produce the Diurnal Variation of the Normal 

 Terrestrial Magnetic Field, by F. H. Bigelow (introduced by C. 

 Abbe) ; Abstract of Results from the United States Coast and Geo- 

 detic Survey Magnetic Observatory at Los Angeles, Cal. , 1882-1889,. 

 Part III., Differential Measures of the Horizontal Component of 

 the Magnetic Force, by C. A. Schott ; On the Anatomy and Sys- 

 tematic Position of the Mecoptera, by A. S. Packard; On the Laws- 

 of the Variation of Latitude, by S. C. Chandler; On the Causes of 

 Variations of Period in the Variable Stars, by S. C. Chandler; On. 

 the Force of Gravity at Washington, by T. C. Mendenhall ; On the 

 Recent Variations of Latitude at Washington, by T. C. Menden- 

 hall ; On the Acoustic Properties of Aluminum, with Experimental 

 Illustrations, by A. M. Mayer; Disruption of the Silver Haloid 

 Molecule by Mechanical Force, by M. Carey Lea (introduced by 

 G. F. Barker) ; On the Homologies of the Cranial Arches of the- 

 Reptilia, by E. D. Cope; On the Osteology of the Genus Anniella, 

 by E. D. Cope; The Astronomical, Geodetic, and Electric Conse- 

 quences of Tidal Strains within an Elastic Terrestrial Spheroid,, 

 by C. Abbe; Asiatic Influences in Europe, by E. S. Morse; Exhi- 

 bition of Chladni's Acoustic Figures Transferred to Paper without 

 Distortion, by A. M. Mayer; On Electrical Discharges Through 

 Poor Vacua, and on Coronoidal Discharges, by M. I. Pupin (intro- 

 duced by T. C. Mendenhall) ; Biographical Memoir of William 



