SCIENCE.-SUPPLEMENT. 



FRIDAY, JUNE 3, 1887. 



ADVANCES IN METEOROLOGY. 



During Mr. William Ferrel's service as a pro- 

 fessor in the signal office for the past few years, 

 from which he has recently retired, his chief 

 occupation was the preparation of a work on 

 meteorology that should represent the modern 

 attitude of the science, and serve as a guide in the 

 theoretical questions that continually arise in the 

 prosecution of the practical studies of our weather- 

 bureau. The book, originally intended to be a 

 ' professional paper,' now appears as an appendix 

 to the late chief signal officer's last report, pub- 

 lished by authority of the secretary of war. This 

 form of publication involves some inconveniences : 

 the making of the book is not so good as such a 

 book deserves; the current page-heading, 'Report 

 of the chief signal officer,' is an unfortunate ex- 

 ample of formality ; but the matter of the book 

 is a long way beyond that of any English work 

 on the subject, and it will take and hold the place 

 of a standard authority. 



Its mathematical treatment of the subject car- 

 ries it beyond most readers. A more popular 

 work by the same auther would be a boon to 

 teachers and students alike, and would do more 

 than this advanced treatise can, to correct the 

 misconceptions that still prevail in most text- 

 books, and to induce a consideration of deductive, 

 dynamical meteorology as well as of inductive, 

 statistical meteorology, that now takes so large a 

 share of the scholar's time. 



The problem of the genei-al circulation of the 

 atmosphere serves particularly well to illustrate 

 the need of this change of view. It is, moreover, 

 a subject in which Professor Ferrel holds a pecul- 

 iarly high position. 



Instead of attempting to review all of the ' Re- 

 cent advances,' I shall therefore refer only to this 

 great problem, whose successful solution illus- 

 trates the high value of our author's methods. 



First, some thirty years ago, Ferrel made the 

 initial steps towards its rational solution ; and, 

 with a single exception, there has been no one 

 else working in this profitable field until a few of 

 the European mathematical meteorologists lately 

 entered it. 



A short acquaintance with the study will suffice 

 to show that the temperature, pressure, and mo- 

 tion of the atmosphere must be closely interde- 



pendent. Difference of temperature, as between 

 equator and poles, must bring about difference of 

 pressure ; difference of pressure will cause winds ; 

 and the winds would soon restore equilibrium, if 

 the difference of temperature were not continually 

 maintained. The equilibrium cannot be reached : 

 the winds will flow in obedience to residual dif- 

 ferences of pressure that they cannot reduce to 

 zero as long as the sun shines. 



The early attempts at the further solution of 

 this problem generally led to the statements that 

 the warmth of the torrid zone caused the equatorial 

 belt of low pressure ; that the cold of the polar 

 regions ought to cause areas of high pressure 

 there, which were somehow reversed into lower 

 pressures than at the equator, especially in the 

 antarctic regions ; that the belt of high pressure 

 around the tropics was due to the crowding of 

 the upper winds as they overflowed from the 

 equator north and south along the converging 

 meridians. The trade-winds, and the anti-trades 

 above them, wei-e normal members of this general 

 circulation ; but the prevailing west-south-west 

 winds of the north temperate zone, and west- 

 north-west winds of the south temperate zone, 

 were not so easily explained. Dove called them 

 ' equatorial ' winds, and saw the compensating re- 

 turn current in the occasional north-east or ' polar ' 

 winds, which are now known to be ' accidental ' 

 or cyclonic in origin, and quite apart from the 

 general planetary circulation. Maury explained 

 them by supposing a curious crossing of currents 

 at the tropical belts of high pressure. In the 

 torrid zone the equatorial overflow was aloft ; 

 but outside of the tropics it came down to sea- 

 level, and the return current ran aloft, — a most 

 arbitrary and unreasonable hypothesis. Views 

 hardly more logical than these still prevail in many 

 text-books. It is indeed now almost universal to 

 ascribe the tropical belts of high pressure to the 

 convergence of the meridians ; though why the 

 crowding of the air should disappear in higher 

 latitudes, where the meridians converge faster, is 

 not explained. Sprung calls attention, in his ex- 

 cellent ' Lehrbuch der Meteorologie,' to the firm 

 hold that this unphysical explanation has obtained, 

 and wonders at the very slow awakening of me- 

 teorologists to Ferrel's theory. It is unfortunate 

 that a theory so greatly needed has been so ob- 

 scurely published. The Naslwille journal of medi- 

 cine and surgery first concealed it in 1856, Run- 

 Tele's mathematical monthly gave it a more expanded 



