March 13, 1891.] 



SCIENCE. 



i=;r 



3. These Conditions extend far above our Highest Mountains. — 

 We find the fluctuations of air-pressure on the advance of these 

 conditions the same at mountain stations as at the base, except 

 that the changes occur later at the summit, for reasons which 

 have been fully set forth in the " Report of the Chief Signal Officer 

 for 1882." The temperature changes, both the rise on the advance 

 of a storm and the fall in its rear, after the diurnal range has been 

 eliminated, are greater on a mountain than at the base, and they 

 occur several hours earlier at the summit. The form which a 

 storm or high area assumes is that of a disk with a height of five 

 to ten miles, and a diameter of one thousand, and it may extend 

 to the limits of the atmosphere. 



3. There is no Marked Movement of Air or Moisture-Particles 

 by Heated Currents from the Earth upward. — The best proof of 

 this, perhaps, is in the fact that the velocity of the horizontal cur- 

 rents is markedly increased as we rise in the atmosphere, and hence 

 such a movement would be rapidly disintegrated and brought to 

 nought. 



4. There is no Whirl in Either of These Conditions a Few 

 Thousand Feet above the Earth. — Observations on Mount Wash- 

 ington (6,300 feet) have shown this fact. Unfortunately we have 

 not the data to show just how high the gyratory circulation which 

 we observe at the earth's surface extends, but the limit is probably 

 3,000 feet. This fact is a most important one to determine, and 

 there is no better region to establish it on the whole earth than 

 the isolated mountain-peaks of New England. Greylock, Ascutney, 

 Killington, Mount Washington, Green Mountain, and a score of 

 others, are all situated right in the path of our storms and high 

 areas, and, it is believed, are destined to aid most materially in 

 solving the riddles which now confront us on all sides. 



5. Their Motion is Independent of the Wind. — To those familiar 

 with weather science this will be self-evident, but it may be well 

 to simplify this proposition slightly. Let us consider the case of 

 a storm condition moving at thirty miles per hour between two 

 points (A and B) six hundred miles apart. Let the wind have a 

 velocity of fifteen miles per hour. In twenty hours the exact 

 changes of the wind, pressure, temperature, etc., which took place 

 at A will take place at B, provided the storm remains constant; 

 but if we had put in the wind at A a. bit of cotton, or some sub- 

 stance which would go exactly with the wind, at the moment the 

 storm-centre was at A, we would have found it just half way be- 

 tween A and B at the moment the storm-centre crossed B. This 

 shows plainly that all the conditions which accompany a storm 

 are practically independent of the wind. The wind blows cold, 

 but it is because a cold wave has passed that way. This may be 

 made still clearer by considering an enormous sphere a thousand 

 or two thousand feet in diameter, and highly heated, at a few 

 thousand feet above the earth. If this were stationary, our ther- 

 mometers, if delicate enough, would show its pressure, and the 

 wind would transport the heat at its velocity ; though it is evident 

 that there would be an exceedingly rapid dissipation of this heat 

 if there were no method of renewal. Suppose this sphere were 

 transported horizontally at thirty miles per hour, and its heat 

 ■could affect our thermometers instantly : it is evident that there 

 would be a miniature warm wave travelling across the country at 

 thirty miles per hour; but this would be independent of the wind, 

 though it would have a tendency to modify that. 



6. Their Motion is Independent of Air-Currents at any Eleva- 

 tion. — This proposition will be the most difficult of all to accept, 

 and yet it seems to be abundantly borne out by the facts. During 

 the passage of a storm, the air-current gradually increases in 

 velocity as we rise in the atmosphere. After a certain height is 

 reached, the velocity of this current is diminished. Again, during 

 the passage of a high area the velocity of the current itself is 

 markedly diminished, and, as I have shown, it is half that of the 

 high area at the height of Mount Washington, while during the 

 passage of a storm it is nearly double the storm velocity. Now, 

 it is plain that any condition having any height in the atmosphere 

 would be entirely disintegrated by the varying velocity of the 

 different strata of the atmosphere; and also its motion cannot be 

 due to that of the strata, since this velocity is far greater than 

 that of the storm, and is only half that of a high area. It has 

 also been shown that the direction of motion of storms and high 



areas is very different from that of the strata far above the earth. 

 One other consideration may be presented. It frequently occurs 

 that storm conditions seem to be transferred through the air with- 

 out a corresponding depression at the earth's surface, and at a 

 velocity which appears to be far higher than the air strata can 

 have. 



This whole subject is exceedingly complicated; and it must be 

 confessed that we must continue to grope rather in the dark 

 until we can obtain the facts which shall enable us to lay the first 

 stone of a consistent theory of these conditions, which are so 

 familiar to us, but of which we know next to nothing. I cannot do 

 better than to close this discussion, without further comment, with 

 the remarkable views of two specialists eminent in this line of 

 research. These views are entirely at variance with the facts 

 observed in this country, and cannot possibly be accepted as an 

 explanation of the phenomena in question. I have already 

 shown, that, owing to the peculiar position of European moun- 

 tains far to the south-east of the path of storms, we can hope for 

 but little assistance from observation at their summits in eluci- 

 dating these complex problems. 



Dr. J. Hann of Vienna, in a recent publication, has said, " The 

 forces which are in activity in the winter in the air circulation of 

 the higher latitudes arise from the heat of the tropics ; that is, 

 from the heat difference between the polar regions and the equa- 

 torial zone. Storms and high areas are merely secondary phe- 

 nomena in the general atmospheric circulation.'' 



Dr. W. Siemens of Berlin has written as follows: "Minima and 

 maxima of air-pressure (storms and high areas) are consequences 

 of the temperature and velocity of air cuiTents in the higher at- 

 mospheric strata." H. A. Hazen. 



Waabington, March 9. 



BOOK-REVIEWS. 



Constructive Steam-E^igineering. By J. M. Whitham. New 

 York, Wiley. 8°. $10. 



This descriptive treatise covers pretty thoroughly a rather ex- 

 tensive field, embracing as it does engines, pumps, and boilers, 

 with all their accessories and appendages. The scope of the work 

 is limited, as indicated by the title, to constructive features, de- 

 sign not being discussed. But this does not lessen the value of 

 the book, as nearly every form of engine or boiler that has won 

 recognition in modern steam-engine practice is fully described, 

 illustrated, and discussed. Steam-engine design, as a separate 

 subject, was ably treated in a previous work by the same author, 

 noticed in these columns a year or more ago. 



In the preparation of this work the author has had ample re- 

 sources to draw upon; and he has exercised notable discretion in 

 sifting out essentials from non-essentials in dealing with the mass 

 of material placed at his disposal by the current literature of the 

 subject. 



The plan of the work is as follows. A brief classification of the 

 various types of engines comes first. This classification may be 

 summed up as (1) condensing and non-condensing; (3) non-ex- 

 pansive and expansive; (3) simple, compound, triple-expansion, 

 and quadruple-expansion; (4) single-acting, double-acting, and 

 rotary; (5) rotative and reciprocating; (6) stationary, portable, 

 locomotive, and marine. Less important is the further classifica- 

 tion into (7) horizontal, vertical, inclined, and oscillating; and (8) 

 erect vertical, inverted vertical, direct-acting, indirect-acting, and 

 beam engines. Exception may be taken to the author's state- 

 ment, in this introductory chapter, that compound, triple, and 

 quadruple expansion engines have respectively two, three, and 

 four cylinders. Some of them have, as shown in a subsequent 

 chapter, at least one extra cylinder; that is, two low-pressure 

 cylinders instead of one larger one. This, of course, is a small 

 matter; but it would be well to classify the engine in this respect 

 by the number of expansions instead of the number of cylinders. 



The second chapter, a very important one, is devoted to heat 

 and steam, embracing a discussion of thermometers and calorim- 

 eters. Then comes a chapter in which the constructive details of 

 an engine are illustrated and discussed; after which comes a lucid 

 presentation of the indicator and its uses, and a chapter on the 



