204 



SCIENCE. 



[Vol. XXI. No. 532 



To my mind, it is impossible to conceive of a normal storm, 

 seeming to move at the rate of 30 or 40 miles per hour along the 

 earth, which does not have a higher temperature up to a height 

 of at least 5 miles, and probably much higher. The reverse of 

 this must also be true in the case of a high area. In fact, I 

 utterly fail to see bow an area of high pressure can have a rapid 

 motion unless in its centre there is denser air, brought about by a 

 greater degree of cold, and this, as I understand it, is exactly the 

 view of Professor Ferrel. These views were generally held up to 

 1886, and I am not aware that any one disputed them, except as 

 regards the pure convection hypothesis. 



In 1886 M. Dechevrens wrote a paper in which he tried to show 

 that the usual law of the relation of pressure and temperature at 

 the earth's surface was exactly reversed at the height of Mount 

 Washington (6,279 feet), and that at that point a fall in tempera- 

 ture occurred with a fall in pressure, and vice versa. This was a 

 most astonishing result, and seemed to disprove the whole con- 

 vection hypothesis. His research consisted in studying the 

 pressure and temperature fluctuations at the summit without any 

 reference to the passage of storms or high areas at the base. 



In this study he ignored the fict that after the passage of a 

 storm the cold wave following would tend to contract the air 

 below the summit, and hence the pressure would continue to fall, 

 and the minimum would not be reached till some time after the 

 passage of the storm at the base. Exactly the reverse cnnditions 

 would be found on the passage of a high area. A full analysis 

 of this proposition, with curves showing these effects, will be 

 found in Annual Repl., Chief Signal Officer, 1882, pp. 897-902. 



In addition to this ditiSculty in comparing these fluctuations 

 directly, there is another almost as serious, which lies in the fact 

 that the maximum and minimum points in the temperature oscil- 

 lations occur several hours earlier at the summit than they do at 

 the base. It will be seen readily that both these conditions would 

 tend to bring the minimum of temperature at the same time as 

 the minimum of pressure at the summit. How closely these 

 conditions of temperature at the base agree with those at the 

 summit we have already seen perfectly demonstrated in the curves 

 given above. This paper of Dechevrens was translated and pub- 

 lished with comments dissenting strongly from the views advanced 

 in the American Meteorological Journal, August, lti86 pp. 297- 

 314. 



It is probable that these researches would have attracted very 

 little attention had it not been for a study by Dr. Hann of obser- 

 vations at Sonnblick (10,170 feet) on almost exactly the same 

 lines as those pursued by Dechevrens, and with the same result. 

 The first paper by Dr. Hann was published in April. 1887, in the 

 Meteorologische Zeitschrift, and this was followed by others in 

 the same and other journals, the last and most thorough research 

 of all, of 86 pages, appearing in April, 1891. In this study the 

 conditions were still farther complicated, from the fact" that 

 Sonnblick lay in southern Europe, where very few, if any, nor- 

 mal storms or high areas pass. High areas, with a pressure of 

 30.7", have been known to hover over this region for three weeks 

 at a time. Such conditions are unheard of in the United 

 States, and their effect can be at once recognized by comparing 

 the fluctuations in the lowest series of curves with those in the 

 other two in the diagram already given. It is easy to see that 

 under such conditions the stagnant air above would become ab- 

 normally and cumulatively heated day by day, while the lower 

 air in a clear sky would be abnormally cooled, and there would 

 at times appear to be a reversal of temperature. With all these 

 disadvantages, however, it will be seen that the temperature 

 curve at the base of Sonnblick, in its larger oscillations, agrees 

 almost exactly with that at the summit. 



One of the most remarkable results found by Dr. Hann was 

 that the maximum and minimum points of temperature lag a 

 day behind those of the maximum and minimum air-pressure. 

 It seems almost incredible that such a deduction could have been 

 made. It seems as if it could only have been by confusing or 

 comparing the minimum air-pressure oscillalian of a.storrn with 

 the minimum temperature oscillation of the following high area. 

 An examination of the diagram already given brings cut this fact 

 most clearly. In nearly every case, both at Pike's Peak and 



Mount Washington, the minimum of air-pressure occurs a day 

 earlier than the minimum of temperature accompanying the suc- 

 ceeding high area. I am sure that no one will make this mistake 

 on st>udying the diagram. The maximum of temperature accom- 

 pfinying a storm occurs about a day earlier than the minimum 

 of pressure accompanying the same storm. The minimum of 

 temperature accompanying the succeeding high area has nothing 

 whatever to do with the previous minimum of pressure, and a 

 proper study of the diagram shows at once the truth. 



It seems to me my position in this matter is brought out most 

 clearly and distinctly in the last paper by Dr. Hann, of 86 pages, 

 in April, 1891. Speaking of fluctuations of pressure and tem- 

 perature at p. 367, Dr. Hann says: " Filr die Erdoberflache sind 

 dieselben seit Langem bekannt." "For the earth's surface have 

 these been for a long time well knosvn." I am sure that every 

 one will admit that at the earth's surface as a storm comes up 

 the temperature rises and is the highest during the storm. As a 

 high area advances, the temperature falls, and is generally vastly 

 lower during such pressures than during storms, especially in the 

 winter season. On page 370 Dr. Hann gives the temperature 

 conditions during barometer maxima, and on page 375 the con- 

 ditions with minima. The sea level station at the base of Sonn- 

 blick was IschI, and I give here the temperature in both maxima 

 and minima during the colder months. 



Trmperalure at Ischl, Cold Months. 

 Barometer Reading. 



This table stows that at the base of Sonnblick during every 

 month except one the temperature is higher in a maximum 

 barometer reading than in a minimum, and the average difference 

 is 3.8° C, or 5.0" F. This exact and marked reversal of the 

 universal law is very significant -and proves conclusively that 

 there has been either a most serious error in studying or selecting 

 out the different cases, or that the universal law does not hold for 

 this region. 



It would seem that Dr. Hann himself now recognizes the diffi- 

 culty in using these records, for he says, in a paper on Ben Nevis 

 (4,406 feet), Meteorologische Zeitschrift, December, 1893, p. 457: 

 " Wie Herr Buchan schon in seinem ersten Berioht hervorhebt, 

 zeigt auch der Ben Nevis sehr haufig die Erscheinung holier 

 Temperatur und grosser Trockenheit selbst miiten im Winter, 

 sobald er in das Gebiet eines Barometermaximums zu liegen 

 kommt. Es treten dann auch of ter die sogenannten Temperatur- 

 umkehrungen auf, was hier besonders bemerkenswerth ist wegen 

 der freien Lage von Fort William am Meere, welche eine Stagna- 

 tion kalter Luft an der unteren Station ausschliesst." " As Mr. 

 Buchan showed in his first report, very often Ben Nevis has the 

 appearance of higher temperature and greater dryness in winter 

 as soon as a barometer maximum lies in that region. It shows 

 then often the so-called temperature reversal, which here is es- 

 pecially remarkable because of the free position of Fort William 

 on the sea, which prevents a stagnation of cold air at the lower 

 station." The question seems to be clearly set forth in these 

 words, and it is probable that the advocates of the view that in 

 the centre of our high areas there is a rise in temperature at some 

 height above the earth will be willing to stand or fall by the 

 proofs at Ben Nevis. 



