594 



NATURE 



[Oct. 2 1, 1880 i 



Comets iSSo, J and e. — M. Bigourdaa has contiuued his 

 ephemeris of the comet discovered by Schaberle on April 6, but 

 states from observations made at Paris that the intensity of light 

 has diminished much more rapidly than is due to change of 

 distance from the earth and sun ; on September 30 he estimated 

 the comet to be of the same brightness as on May 18 ; it is still 

 in a favourable position for observation, as will be seen from 

 the following extract from M. Bigourdan's ephemeris for Paris 

 midnight : — 



The Astronomer-Royal has notified the discovery of another 

 comet by Mr. Lewis Snift of Rochester, N.Y., on the night of 

 October 11, in R.A. 2ih. 30m. and Decl. + 18°. 



METEOROLOGICAL NOTES 

 Prof. Loom is, in his thirteenth contribution to meteorolog)-, 

 investigates the question of the great and sudden changes °of 

 temperature which are so marked a feature in the climates of a 

 large portion of the United States. Six years' observations of the 

 Signal Service stations have been examined, with the result that 

 there are 118 stations at which there has occurred at least one 

 case of a daily range not less than 40°-o. Limiting the inquiry, 

 however, to stations at which the average number of ca.-es 

 amounted to six annually, it is seen that there are thirty-six such 

 stations. The stations w here the great fluctuations of tempera- 

 ture occur most frequently are situated south of lat. 35", in which 

 region the fluctuations of pressure attending the progress of 

 storms are but little feh ; and it is to be noted that these gi-eat 

 fluctuations of temperature occur most frequently in the summer 

 months. Thus at Wickenburg (lat. 34-0, long. II2°7), which 

 is situated in a desert sandy region, with an annual rain- 

 fall of only 4-99 inches, on ten of the nineteen days ending 

 with August 14, 1S77, the temperature showed a daily range 

 of at least 62°-o, reaching in one case to 76° 'o. The^e 

 enormous temperature changes are due to the extreme dry- 

 ness of the air, by which the sand becomes intensely heated by 

 the sun during the day, whereas by night the loss of heat l^y 

 radiation is as great as perhaps anywhere on the globe. The 

 general result of the inquiry is that the most remarkable cases 

 are merely examples of the ordinary diurnal change of tempera- 

 ture, unaffected by the passage of storms, whilst the reni.iining 

 cases, which occur iu the higher latitudes of the States, are to be 

 ascribed to the influence of storms along with the ordinary diurnal 

 change of temperature. It also appears from a careful investi- 

 gation that dry air, even when greatly heated, has but little 

 ascensional force, and that the violent uprising of heated air, 

 so frequently witnessed in moist climates, particularly during 

 thunderstorms, is mainly due to the large amount of aqueou° 

 vapour with which it is charged. As regards great fluctuations 

 of temperature in winter. Prof. Loomis points out that while, 

 for example, a temperature of - 20° 'o occurs at Denver on the 

 east side of the Rocky Mountains, an average temperature of 

 30-0 prevails in the Salt Lake Basin, and remarks that by the 

 movements of the atmosphere attending the progress of a great 

 storm these contiguous masses of air with temperatures so 

 different from each other are brought successively over the same 

 station, and thus bring about a change of temperature amounting 

 on occasions to 50' -o in a single hour. 



Pkof. Loomis also carefully investigates the storms, with their 

 characteristic low barometers, which cross the Rocky Mountains, 

 and shows that no great barometric disturbances originate in the 

 Salt Lake Basin ; that nearly all the great barometric disturb- 

 ances experienced in the Salt Lake Basin come from the Pacific, 

 and generally from the north-west; and that nearly all these 

 disturbances can be followed to the Atlantic, meeting it near 

 lat. 47°-o, and occupying from two to six days in the passage, or 

 an average of three and a half days, corresponding to an onward 

 movement of about 700 English miles a day. As has been shown 

 to obtain in other regions of the globe, the isobars which define 

 storms are often not so symmetrical over a mountainous region 

 as over a level country. In not a few cases however the isobars 

 show considerable symmetry over the Rocky Mountains, and this 

 feature becomes the more noticeable in very violent storms, 

 i-rom the observations made at Pike's Peak, 14,200 feet high, 



as w'ell as at Mount Washington, 6,285 feet, it appears that the 

 winds at great elevations circulate about a low barometer, just as 

 they do near the level of the sea ; but the position of this centre 

 at great heights sometimes differs considerably from the low 

 centre prevailing at the surface of the earth, and when such ' 

 deviation does occur it is generally toward the north-west. Of \ 

 the thirty-six cases examined, the low centre at great elevation 

 was, m twenty-seven cases, vertical over the low centre at lower i 

 levels, in five cases to north-west, in one case to north, in another ' 

 case to west, and in two cases to east. It must however not be 

 lost sight of that this important point in the phenomena of 

 storms cannot be exactly determined but by a multiplication of I 

 high-level stations. ' 



Displays of auroras appear to have been remarkably frequerrt 

 m America during August last. In Mr. Carpmael's Weather 

 Report of the month for Canada it is stated that the aurora of 

 the 1 2th was very brilliant, and was seen at nearly every station 

 from Manitoba to the Atlantic. From the United" States 

 Monthly Weather Report we learn that auroras were frequent 

 during the month, occurring on no fewer than twenty-one nights, 

 the auroras of the 12th and 13th being of remarkable brilliancy, 

 as well as widespread. On these nights the aurora was seen at 1 

 about loo stations from Maine westward, as far as clear skies 

 allowed its being seen. The more prominent features of these 

 auroras as detailed in the Report are of such interest as to suggest 

 that a more detailed account of them, as seen in the northern hemi- 

 sphere during the night of August 12 and 13, could not fail to 

 contribute data of the greatest importance in this little-understood 

 branch of physics. 



In the JourHal of the Scottish Meteorological Society, 

 recently published, there is a paper of some interest, by Mr. 

 Buchan, on the diurnal periods of thunderstorms in Scotland. 

 There are two well-marked types of thunderstorms, the one 

 occurring in the summer months, and having its daily maximum 

 frequency from i p.m. to 6 p.m., and the other occurring in the 

 winter months, with its maximum from 9 p.m. to 3 a.m. Stations 

 in the eastern division of the country where the annual rainfall is 

 small, or only of moderate amount, have all, or nearly all, their 

 thunderstorms during the summer months ; whereas in the west, . 

 or where the climate is wet and the rainfall heavy, a very con- 

 siderable proportion of the thunderstorms occur during the winter 

 months, and these are nearly ahvays of short duration, and are 

 the accompaniments of the winter cyclones of North-Western 

 Europe. In this connection it is interesting to note that the 

 thunderstorms of Stykhisholm in Iceland are phenomena of the 

 winter months and of the nights, only three being recorded as 

 having happened at a time of the day when the sun was above 

 the horizon. The maximum daily period of the summer thunder- 

 storm coincides with the hours when the ascending columns 'of 

 heated air from the earth's surface are in full activity, and the 

 result is no doubt largely due to the circumstance that these 

 ascending masfcs of heated air develoj) a charge of electricity as 

 their moisture condenses into cloud. The period of maximum 

 frequency of the winter thunderstorm occurs some hours before 

 and after midnight, or during those hours of the day when the 

 land surface presented to the vapour-laden winds of the Atlantic 

 approaches to and reaches its diurnal minimum temperature, and 

 when consequently the condensation of the vapour may be ex- 

 pected to reach its daily maximum. On the other hand, the 

 minimum period in summer occurs during the early morning, the 

 absolute minimum being at the hour just before the ascending 

 columns of heated air are set in motion, and the number remains 

 few- till about II a.m., or till the tops of the heated columns 

 have risen to some height in the atmospheres. 



In the Journal of the Meteorological Society for April and 

 July last are given the results of observations made during the 

 first six months of 18S0 at about forty " climatological stations" 

 recently established by the society. At these stations observa- 

 tions are taken only once a day, [viz., at 9 a.m., and are 

 restricted to temperature, cloud, and rain. An extension of 

 these stations which would include the whole of the English 

 sanataria, and which doubtless will gradually be effected, would 

 furnish data for a correct presentation of the comparative 

 climatologies of the health resorts of England. 



BIOLOGICAL NOTES 

 Nest-Building AMPHiroDs. — Mr. S. J. Smith, in a memoir 

 on some amphipods described by Thomas Say (Trans,, Con- 

 necticut Acad., July, 18S0), states that the tubes which certain 



