April 28, 1892] 



NATURE 



611 



be still greater. In order, therefore, to obtain com- 

 parable values, even for neighbouring stations, it is 

 essential that the data compared should be those of the 

 same interval. 



Both as regards season and amount, the changeful- 

 ness of temperature depends very greatly on local geo- 

 graphical circumstances, so that neighbouring places 

 very often differ greatly from each other. In Europe 

 it increases from west to east and from south to north, 

 in both cases towards the interior of the continent. It 

 increases also on the whole with altitude, but very irre- 

 gularly, being great on exposed plateaux, and compara- 

 tively small on mountain peaks. Places situated in 

 valleys show very great differences, according to their 

 exposure. Among the Austrian stations, those on the 

 southern slopes of the Alps have the greatest vicissitudes, 

 owing to the warmth they acquire in sunny weather and 

 the consequent greater fall of temperature when a change 

 of weather sets in. In general the changes of temperature 

 at high elevations are greater than at low altitudes in 

 summer, but less in the winter season. In the high 

 mountain valleys in spring the changes are much smaller 

 than on the neighbouring plains. 



In the British Isles, Mr. Scott found that the number 

 of rises exceeding 5° between any two consecutive days 

 was greater than the number of falls of the same amount, 

 and also that the mean value of the rises exceeds that of 

 the falls. In Austria, also, except in the Southern Tyrol 

 and on the coasts of the Adriatic, rapid rises are greater 

 than rapid falls in the winter, and less in the summer ; but 

 on the whole the former preponderate. In the south, 

 however, rapid falls are greater than rapid rises at all 

 times of year, and therefore also on the mean of the 

 year. This peculiarity is a still more marked charac- 

 teristic of lower latitudes, since in Northern India it was 

 found that rapid falls are about three times as numerous 

 as rapid rises, and on the whole greater in amount. 



The duration of rises of temperature is somewhat 

 greater than that of falls, and both are rather greater at 

 mountain stations than at low levels. Thus the passage 

 of a wave of temperature, on the mean of the two 

 stations Klagenfurt and Salzburg, occupies, on an average, 

 4*56 days, on the Sonnblick 4*93 days ; or, in other words, 

 6i waves pass within the month at the higher and 7 at 

 the lower stations. The longest period of continuous 

 cooling that occurred at any station was ten days at the 

 mountain observatory of Hoch Obir, and the longest 

 continuous rise of temperature ten days at Klagenfurt. 

 There is a marked annual periodicity in the length of 

 the temperature waves, with two epochs of maximum, 

 viz. in March and September, and two of minimum, in 

 July and December. From the data afforded by certain 

 stations in Austria and Saxony, Ur. Hann computes 

 the following formula for their annual variation in Central 

 Europe— 



4-813 4- 0-138 sin (26° 45' + x) + 0-164 sin (318° 27' -f-2x). 



The last subject investigated in Dr. Hann's memoir is 

 the question whether the inter-diurnal changefulness of 

 temperature shows any periodical variation during the 

 sun-spot period ; for which purpose he takes the 90 

 years' registers of Vienna, Wilna, and Warsaw. He 

 finds that on the mean of these stations a certain minute 

 variation is indeed apparent, but it is one of two ma.\ima 

 and two minima, and the whole range is so small that it 

 is doubtful whether it is other than fortuitous. 



In the foregoing paragraphs only a few of the more 

 important results of Prof. Hann's investigation have been 

 noticed. His memoir contains many others of interest, 

 well worthy of study, and forming important contributions 

 to general climatology ; and like the original memoir, 

 pubhshed seventeen years ago, it will doubtless stimulate 

 others to prosecute the subject. It is especially import- 



NO. I I 74, VOL. 45] 



ant from a medical point of view that the statistics of all 

 health resorts should be analyzed in the manner of which 

 Prof. Hann has here given so admirable an example. 



H. F. B. 



FORESTRY IN AMERICA} 



T T cannot be said that, as far as the issue of reports 

 ■^ and pamphlets on forestry is concerned the Agri- 

 cultural Department at Washington has been idle ; if 

 only this activity would resolve itself into the estab- 

 lishment of a State Forest Service, and the formation of 

 State forests out of the wreck of the former forest wealth 

 of North America ! 



An important series of papers on forest matters has 

 come to hand, and though they date as far back as 

 1889, they are probably new to many of the readers of 

 Nature. 



The first paper is by Dr. James, Professor of Public 

 Finance and Administration in the University of Pennsyl- 

 vania, and is entitled " The Government in its Relation 

 to Forests." The Professor has evidently studied his 

 subject thoroughly, and the remedy he proposes is the 

 exact counterpart of that which has been so successfully 

 applied to the forests of India. He commences by stating 

 that the forests of any large country not only constitute 

 a large portion of its wealth, but form the indispensable 

 basis of a flourishing manufacturing and commercial 

 industry. They are also one of the most important 

 elements in determining the climatic conditions of a 

 region, and, through these, the distribution of the popula- 

 tion, of industrial pursuits, and of disease and health. 

 He states that the value of the forest crop in the 

 United States in 1880, the census year, was 700,000,000 

 dollars (= ;,^ 140,000,000), and that if the value of the total 

 annual output of the mines, quarries, and petroleum wells 

 were added to the estimated vakie of all steamboats and 

 other craft on American waters, it would still be less than 

 the value of the forest crop, by a sum sufficient to purchase 

 all the canals, telegraph companies, and construct and 

 equip all the telephone lines in the States. 



He then shows how Government has fostered agricul- 

 ture by offering land on easy terms, by establishing 

 model farms and agricultural schools, by improving the 

 breed of stock, by free distribution of seed, and in many 

 other ways ; it has also assisted manufactures by the 

 protective tariff, bounties, and exhibitions, &c. ; and 

 that vast sums have been spent by the State on improving 

 rivers and harbours, and on the general means of com- 

 munication — railroads and roads. Game and fish are 

 also protected by the State, but although from their 

 forests the Americans have been drawing more natural 

 wealth than from all other sources together, yet practi- 

 cally nothing has been done to preserve them from the 

 devastations of selfish people. Besides the great demands 

 on the forests for timber, three-fifths of the people in 

 the States use wood for ordinary domestic fuel, and the 

 value of the wood fuel annually consumed is placed at 

 325,000,000 dollars. 



Prof. James then treats at length of the vast indirect 

 value of forests in maintaining a steady supply of water 

 in rivers, and preventing floods. He shows that the 

 maintenance of a system of factories and mills dependent 

 on a watercourse becomes impossible when the stream 

 is converted into a mountain torrent for one quarter of 

 the year and is all but dry during another quarter ; and 

 instances the River Schuylkill, from which Philadelphia 

 draws its water-supply, where the current has become 

 too shallow and sluggish to carry off the ever-increasing 



I " Department of Agriculture, Forestry Division. Bulletin No. 2.— Re- 

 port on the Forest Condition of the Rocky Mounuins, and other Papers." 

 With a Map showing location of Forest Areas. Second Edition. (Washing- 

 ton : Government Press, 1889.) 



