SCIENCE. 



[Vol. XIV. No. 340 



Tient. I shall therefore make further mention only of the cyclones 

 and cyclonic storms concerning which the information is full and 

 important. It may be recalled that Redfield early recognized the 

 general occurrence of cyclonic whirls, seeing that high velocities 

 were in no wise essential in their circulation, and that our ordinary 

 ■changes of Weather and shifts of wind were to be regarded as 

 closely related to the hurricanes of the West Indies and other 

 tropical regions. There has been and still is a conservative hesita- 

 tion to accept so large a generalization, an illustration of which is 

 -commonly seen in the slowness of weather services in general to 

 use such a term as " cyclonic " in connection with the " lows," 

 " areas of low barometer," " barometric depression," " barometric 

 minima," and other paraphrases in current use. The demonstra- 

 tion of the occurrence of relatively gentle cyclonic storms in India, 

 and at seasons hitherto regarded as exempt from them, is therefore 

 ■of particular interest not only as a fact, but also in the historic de- 

 velopment of the science. 



As regards the cyclones themselves, little is here said in the way 

 ■of theory. For that the reader should go to the excellent studies 

 ■on individual cyclones, chiefly by Eliot, in the memoirs of the In- 

 <lian meteorological department. But the incurvature of the storm 

 winds is clearly stated ; and, while full justice is done to the tire- 

 less labors of Piddington in earlier decades, the errors into which 

 he was led by following the " eight-point rule," or circular theory 

 ■of storms, are explicitly pointed out. The true seasons of occur- 

 rence, the relative rarity of these storms, their extreme violence, 

 their tracks and moderate progressive velocity, their general failure 

 to cross even the southern point of India, and the advances lately 

 made in announcing their approach, are all well treated. Until 

 within a few years, it was only the violent cyclones of the May and 

 ■October seasons, originating on the Bay of Bengal, that were un- 

 ■derstood when Indian cyclones were mentioned ; but with the es- 

 tablishment of a system of observing stations, and, still more, with 

 the preparation of daily weather-maps, it has become apparent that 

 •cyclonic storms occur in India at other months also, and of moder- 

 ate intensity. Blanford recognizes the essential identity of the two 

 in origin and constitution ; but he thinks it advisable to distinguish 

 them as cyclones proper and cyclonic storms, in order to avoid 

 ■misapprehension as well as to emphasize their differences. While 

 the former are practically limited to the late vernal and autumnal 

 months, and not more than two violent ones occur in an average 

 year, the latter occur in frequent succession all through the rainy 

 summer monsoon, and also bring the winter rains to northern In- 

 ■dia. Curiously enough, the cyclonic storms of summer advance 

 toward some point between west and north, while the winter 

 •storms move eastward, or even a little south of east. Here is cer- 

 tainly a new characteristic of this interesting region, and, as far as 

 I know, it is not matched in any other part of the world. It is 

 ■presuitiably an effect of alternation from a torrid to a temperate 

 position in the general circulation of the atmosphere. Two of these 

 storms are illustrated by weather-charts of several successive days, 

 in which the central barometric depression and' the general spiral 

 movement of the surface winds are clearly indicated. In one of 

 the winter cyclonic storms — that of late January, I S83 — there was a 

 ■distinct sequence of weather changes with the eastward advance of 

 the storm-centre, precisely of the kind that we know so well in 

 these latitudes, — in the front, warm, damp, southerly winds, clouds, 

 and rain or snow ; in the rear, north-westerly winds, clear sky and 

 low temperature, a veritable " cold-wave," giving some hill stations 

 their lowest thermometric records. If this sort of thing is typical 

 of Indian winters, it is likely that our term "cold wave" will go 

 into use there, as their term " cyclone " has come to be so valuable 

 with us. 



Again, as to the conditions permitting rainfall. While it is under- 

 stood that rain often occurs independently of cyclonic conditions, 

 — as, for example, the diurnal summer rains of Florida or of 

 mountain-peaks, — it appears, from the weather-maps of this coun- 

 try and Europe, that most of our precipitation is cyclonic, either in 

 widespread rains or snows, or in local thunder-showers, whose oppor- 

 tunity is in good part dependent on cyclonic winds and contrasts of 

 temperature thus induced. Now, the same thing appears in India. 

 Rain there also may be independent of cyclones and cyclonic storms, 

 as at Cherrapunji, on the foot-hills of the Himalaya north of the Bay 



of Bengal, where the annual rainfall is nearly fifty feet deep, where 

 from April to September there are on the average twenty-five rainy 

 days in a month, and where 40.8 inches of rain have been collected 

 in twenty-four hours (June 14, 1876). Here much of the rain may 

 be " topographic," a re-action of the mountains on the winds ; but, 

 as a rule, Indian rainfall is, like ours, cyclonic. The " bursting 

 of the monsoon" is an accompaniment of a summer cyclonic 

 storm ; and the alternation of rain, showers, and occasional rain- 

 less days in July and August, is but the expression of the passage 

 of a series of summer cyclonic storms. This gives an entirely new 

 aspect to the monsoon rains. All the excessively heavy rains, for 

 which northern India is remarkable, are cyclonic rains, even though 

 recognizable in their true character only when synoptic weather- 

 charts are constructed. 



Sind, a dry district in the far north-west, with an annual rainfall 

 only from five to ten inches, and with only from thirteen to thirty 

 rainy days in the year, also is dependent on the cyclonic storms. 

 Rain falls only when, in the summer monsoon, a cyclonic storm 

 comes in from the eastward, and travels as far as Sind before it is 

 broken up ; or when, in the winter, one forms in Sind, or passes 

 eastward across it from Baluchistan. 



This is certainly a most significant extension of Redfield's acute 

 suggestion. Disturbances in the general atmospheric circulation 

 tend to take the form of convectional whirls, and give forth rain. 

 If the conception of the whirl ■ is rigid and artificial, it will be of 

 little advantage ; but if it admit the unsymmetrical irregularities so 

 abundantly illustrated on our weather-maps, it must come to be one 

 of the most significant generalizations that meteorology has brought 

 forth. 



Recalling what the meteorological department of India has be- 

 come under Mr. Blanford's direction, and remembering the high 

 value of his writings on meteorological subjects, we can but wish 

 that his future leisure might be directed to a general work on 

 meteorology, of scope as broad as Schmid's " Lehrbuch," but with 

 the statistical flavor of that book replaced by the physical flavor 

 that characterizes modern meteorology. There is no such work in 

 English, although such a work would have many English readers. 



W. M. D. 



Numbers Universalized : An Advanced Algebra. By DAVID M. 

 Sensenig. New York, Appleton. 12°. 



This volume will eventually form the first part of a higher 

 algebra, soon to be completed, being intended as an advanced 

 elementary algebra. The object in issuing it separately, as we are 

 informed in the preface, is " to meet the wants of such schools as 

 have arranged a higher course in algebra than is outlined and 

 treated in the author's first book, ' Numbers Symbolized,' and yet 

 have not time enough to devote to this branch of mathematics to 

 complete a full course in higher algebra." The book is well 

 adapted to meet the requirements of schools in which students are 

 prepared for entering college, as well as of advanced classes in 

 high and advanced schools. 



In his treatment of the subject, the author, who is professor pf 

 mathematics in the State Normal School at West Chester, Penn., 

 has aimed to carefully keep intact the logical sequence of thought, 

 avoiding unnecessary difficulties in the discussion, on the one hand, 

 and too great simplicity, on the other. The definitions are well 

 arranged, and concisely expressed in language unusually simple 

 and exact ; and illustrations are given only when required by con- 

 cepts not sufficiently clear without them. The work as a whole is 

 in line with the best school methods now in use, and should be ac- 

 ceptable to students as well as teachers. 



AMONG THE PUBLISHERS. 



The supplement to Harper s Weekly of July 24 is devoted to 

 the progress made in electric lighting in New York City, the sub- 

 ject being ably treated by Schuyler S. Wheeler, electric expert of 

 the Board of Electrical Control. Mr. Wheeler discusses and ex- 

 plains the subject under the heads of " Generating and Distribut- 

 ing," "Lamps," "Systems of Distribution," "The Alternating 

 Current," and " Construction of the Lines." The article is fully 

 illustrated. 



