November 2, 1S93] 



NATURE 



15 



ground. There is, on the other hand, evidence that an epidemic 

 caused the plague to come to an end. But it is the general 

 opinion of the farmers and shepherds of the district from which 

 Mr. Adair obtained his particulars, that the disappearance is due 

 in a great measure to the work of such natural enemies as 

 the owl, kestrel, rook, blackhead gull, and buzzard, the stoat, 

 and the weasel. 



The Weather Bureau of Washington has published an 

 elaborate discussion of the climate of Chicago, by Prof. H. A. 

 Hazen, being No. lo of the valuable i)«//^/2/fj now being issued 

 by that department. The city of Chicago is situated at the 

 soath-west of Lake Michigan, whose elevation is about 580 feet 

 above the level of the sea. The earliest observations available 

 were made in 1832, and continued until 1836, after which time 

 they were of a very fragmentary character until November, 1859, 

 since which a continuous series of observations has been 

 maintained, at least as far as regards the temperature. The 

 lake has naturally great influence upon the climate, and this has 

 been investigated in great detail for each separate element. 

 With regard to the winds, the tables show that for the year there 

 is a maximum from the south-west, and- a secondary maximum 

 from the north-east. Daring the cold months there is a marked 

 preponderance of land winds, while in the warm months there 

 is a slight preponderance of lake winds. The mean temperature 

 deduced from twenty years' observations is 48^ '6, and occurs 

 about the third week in April and October. The highest 

 temperature occurs about the middle of July, and the lowest 

 the third week in January; for 174 days the temperature is 

 rising, and during 191 it is falling. The cold spell about the 

 middle of May, which is generally observed in the northern 

 hemisphere, is well marked in the 5 - day means. The highest 

 temperature observed was 99' '6 on July 17, 1S87, and the 

 lowest -23" on December 24, 1872. The maximum tem- 

 piratare was 90' or over on 121 days during 20 years, and 

 a minimum temperature of -15" or below was only reached 

 16 times. Accurate rainfall observations can scarcely be said 

 to begin at Chicago before 1S67. The annual rainfall from this 

 series is 34*4 inches, and is fairly well spread over each month. 

 A fall of 2 '5 inches in a day only occurred 15 times in 20 

 years. The work contains an abstract of the observers' jfournal 

 since the occupation of the station by the Weather Service, 

 which includes an interesting account of their experience of the 

 great fire of October 8-9, 1871. 



We learn from the report on the administration of the ISIeteo- 

 rological Department of the Government of India that the 

 valuable series of meteorological observations which were taken 

 by the late Mr. J. Allan Broun at Trevandrum during the years 

 1853-64 are being prepared for publication by that department, 

 owing to the action taken by the Royal Societies of London 

 and Edinburgh, and by the Meteorological Council with that 

 view. It is proposed to publish them in three volumes contain- 

 ing (i) hourly observations, (2) comparative observations at 

 various stations on the jTravancore Hills, and (3) discussion of 

 ihe observations. The report shows great activity in the collec- 

 tion of observations from ships entering the Hooghly ; these 

 observations are used in the construction of daily charts of the 

 Indian land and sea area, the publication of which began with 

 January this year. The growing usefulness of ordinary weather 

 forecasts is exemplified by the fact that they have been extended 

 to expeditions in the field, and they have been pronounced by 

 the military authorities to have been very successful. 



Herr p. Czermak publishes, in Wiedemann^ s Atinahn, some 



beautiful photographs of ascending currents in gases and liquids. 



I'or the former a box of rectangular section was used, consisting 



of plate-glass sides firmly cemented together. At the centre of 



NO. 1253, VOL. 49] 



the bottom was placed a flat spiral, the escape spring of a large 



spindle clock. The spiral could be heated by the passage of an 

 electric current. A glass tube opened into the box at the bottom, 

 directed towards the centre, for the introduction of smoke. A 

 second glass tube led in at the top, for ventilation or the intro- 

 duction of a light gas. Tobacco smoke blown in through the 

 lower tube was seen to spread out on the bottom in a uniform 

 layer, provided all parts of the box were at the same tempera- 

 ture. The touch of the hand on one side was sufficient to 

 produce an ascending current and a motion of the smoke 

 towards the warmer side. It was therefore necessary lo perform 

 the experiments in a room kept at a uniform temperature. On 

 sending a current through the spiral, the mushroom-like figure 

 first described by Vettin was observed to rise in faultless sym- 

 metry. This was photographed by flash-light, and the repro- 

 ductions show the spiral convolutions to great perfection. Since 

 the contours reflected the greatest amount of light, they stand 

 out well from the dark background, and clearly exhibit the in- 

 terior structure of the stream-figure. In order to imitate more 

 closely the actual condition of the atmosphere during the ascent 

 of warm air currents, the upper part of the box was filled with 

 coal-gas. The stream-figure then ascended in the usual manner 

 until its vertex reached the lighter stratum. It then became 

 stationary, expanded in the diffusion stratum, and part of the 

 smoke trickled back to the bottom. Sometimes it was found 

 possible to obtain a cloud-like structure, with a dome in the 

 centre and wavy outlines. The figures were more easily pro- 

 duced and photographed in the case of liquids, but the general 

 type remained the same. 



Investigations are carried on at the Agricultural Experi- 

 ment Station, Purdue University, Indiana, on much the same 

 lines as at Rothamsted. Bulletin 45 of the Station contains in- 

 formation of interest and importance concerning wheat-growing 

 in Indiana. From field experiments extending over ten years 

 it appears that none of the varieties of wheat tried have any 

 tendency to deteriorate or "run oat," provided proper care is 

 exercised. No wheat proved to be "rust-proof," bat early 

 wheats were generally less injured by rust than later kinds. 

 Eight pecks of seed per acre gave the best returns at the Station, 

 the average yield for nine years being 30-35 bushels per acre. 

 The best results came frooi sowings made not later than Sep- 

 tember 20. The value of crop rotation in maintaining yields 

 of grain has been strongly emphasised, for a comparison of ro- 

 tating crops with constant grain-cropping for seven years showed 

 an average gain of 57 bushels per acre in favour of the former. 

 Another important result obtained was that wheat may be har- 

 vested at any time from the dough stage to the dead-ripe condi- 

 tion, without appreciably affecting the weight or yield of the 

 grain. Finally, a compafison of forms of nitrogen as fertilisers 

 for wheat indicated that sulphate of ammonia is better than 

 nitrate of soda or dried blood. 



I.\ a former note (June 22, 1893) we have given a sho r 

 account of the means employed by Signor Augusto Righi to 

 obtain electro-magnetic waves of small wave-lengths (about 

 8 cm.), and also on p. 299, vol. xlviii. we have described some 

 of the experiments he has performed, using waves of this small 

 wave-length. Since then Righi has continued his researches, and 

 has published in the Proceedings of the Royal Academy of 

 Lincei an account of his experiments on the question as to 

 whether the electric force is perpendicular to, or in the plane of 

 polarisation. Trouton, from his experiments on the reflection of 

 electro-magnetic waves from the surface of non-conductors, such 

 as glass and paraffin, has come to the conclusion that the electric 

 force is perpendicular to the plane of polarisation. The reflection 

 of these waves from paraftin.and also from metals,has been studied 

 by Righi, who finds a marked difference in the two cases. In the 



