FOREST AND STREAM. 



149 



♦ ' 



INFLUENCE OF FORESTS ON AIR AND 



SOIL, AND THEIR CLIMATIC AND 



HYGIENIC IMPORTANCE. 



* 



TO ascertain by actual scientific observation and meas- 

 urement the influence of forests on the air and soil, 

 and their climatic and hygienic importance, the Bavarian 

 Government instituted at different elevations and in various 

 parts of the kingdom seven forestial and meteorological 

 stations, at each of which, three daily observations are 

 made at two different points, one situated in the middle 

 of a large forest, and the other in the middle of a large 

 field. The results of these observations according to Dr. 

 Ebermayer's report (published by C. Krebs in Aschaffen- 

 burgh, 1873), proves conclusively the marked influence 

 of forests on the temperature of the soil. In the spring 

 and summer months (March till August), the difference in 

 the temperature of the soil of the forest and of the open 

 field averages 7.24 °F, in the months of September, Octo- 

 ber and February this difference falls to 2.75 G F, and du- 

 ring winter months to °0. The observations further show, 

 that although the absolute moisture of forest air in' the 

 course of a year appears to be hardly greater than that 

 of the open field, it is different as to the relative moist- 

 ure, for, as the temperature of the air in forests is on the 

 whole lower than that in the open field, the forest air must, 

 with the same absolute moisture, have a greater relative 

 moisture and be nearer its point of saturation; a determi- 

 nate lowering of temperature will therefore produce in 

 forests a separation of water more readily and in greater 

 quantity, than in the open field. 



This difference of relative moisture is much more marked 

 in high land than in low land, corresponding to the increas- 

 ing values of the difference of temperature between for- 

 est and open air as we rise above the sea level; the 

 reason is that the difference of temperature is greater in 

 summer. This relative moisture of forest air in summer, 

 exceeds that of the air in the open field by a greater amount 

 than in the other seasons of the year. The forest thus 

 makes the climate moister, and more so in summer, in the 

 time of vegetation, than in other seasons. The difference 

 of relative moisture between forest air and field air, was in 

 spring, 5.70° in summer, 6.18°, in autumn, 5.22° and in 

 winter, 5.24°. 



The greater relative moisture in forest air affects 

 the amount of evapnraUon. Observations were made of 

 the quantities of water evaporated from free water surface 

 in forests and in the open fields, and it appears that on an 

 annual average, the evaporation is about 2.7 times smaller 

 in forests than in open fields. On comparing seasons, it is 

 nearly four times greater in summer than in winter, but 

 even in winter there was two and one-half times less water 

 evaporated in the former than in the latter. The differ- 

 ence in the amount of evaporation in the warmest and 

 driest months (July and August) between forests and open 

 air was on an average, 290.28 cubic inches of water for one 

 square foot of water surface. 

 The relative pi\>portion of evaporation, however, does not 

 essentially alter in the several months, as we find that in 

 forests on an average two to three times less water is evapo- 

 rated than in the open air. This great difference in the 

 amount of evaporation probably arises in great part (be- 

 sides the difference of temperature, saturation etc.) by the 

 much weaker movement of the wind in forests.. Of 

 greater practical interest than the evaporation from a free 

 water surface, is that from the ground. As in many parts 

 of Bavaria and Germany generally, the farmers and citi- 

 zens of villages have an old privilege to gather from the 

 forests dry leaves for littering and manuring purposes, not 

 only forest and open field were compared with each other, 

 but also the influence of such litter covering was examined. 

 T e forest alone deprived of its litter covering, diminishes 

 the evaporation of ground water, as compared with that of 

 the open field, about 62°; with litter covering the evapora- 

 tion was further diminished about 22°. In reference to the 

 question " AVhat influence have forests on the quantity of 

 rain in a country, and do they favor the formation of rain 

 or not?" Ebermayer's observations lead him to affirm that 

 in plains of the same general character, the influence of for- 

 ests on the quantity of rain is very small, and that it has 

 also no marked influence on the percentage of distribution 

 of rain. With elevations above the sea level, the impor- 

 tance of the forests as regards influence on the rain 

 quantity increases. On mountains it bas a higher value than 

 on plains. In the summer^season the action of the forest on the 

 rain quantity is much greater in the winter. If we compare 

 the rain fall on one square foot of surface with the quantity 

 of water evaporated from an equal free water surface in the 

 forests and in the open field, it appears that everywhere the 

 annual rain fall is greater than the evaporation. The higher 

 the place is, the greater is the excess of rain and snow 

 water over the quantity evaporated. In the interior of a 

 forest the evaporation is so small, that a much larger 

 quantity of water enters into the soil, than is dissipa ed by 

 evaporation. In the open field most water penetrates the 

 ground in the winter, next during spring and autumn, and 

 least in summer. In summer the quantity of water which 

 passed through the ground was at one foot depth, three 

 and one-half times, at two feet depth, four and one-half 

 times, at four f-iet depth, seven and one-half times less than 

 in winter. 



The forest-covered ground behaves towards water quite 

 differently. In forest ground without litter covering, the 

 quantity of water at one foot depth is greater in winter; 



then follows spring; and in autumn and in summer it, is 

 nearly equal. In litter covered forest ground the quantity 

 penetrating the ground in all the four seasons was nearly 

 equal. If we compare the forest ground with the open 

 field, the quantity penetrating the former is* in winter less 

 than that penetrating the latter. In spring the forest 

 ground at four feet deep gave per three square feet surface 

 about 133.42 cubic inches more water than the unwooded 

 ground. In summer litter covered forest ground gave at 

 six feet depth 1245.71 cubic inches more water per three 

 square feet, than the ground in the open field, while in for- 

 est ground without litter, at one foot depth twice as much 

 water passed through as in the open field. In autumn, 

 lastly, the penetrating quantities of water in the forest and 

 in the open field were nearly epual. 



The action of the forest and of Htter covering on the wa- 

 ter contents of the ground and of the humidity of a region 

 is thus most marked in the warmest season, and in hot 

 countries. The forest produces an equable distribution of 

 the ground moisture in the several seasons of the year. 



In a hygienic point of view, it has been shown that 

 in fever and malaria, contagion is generally carried and 

 communicated by currents of air, but that f crests often 

 act as a protection against them. It was observed that in 

 many localities in India which formerly were free of conta- 

 gious diseases, these appeared after cutting down of the sur- 

 rounding forests. Chas. Plaggi. 



TREE-PLANTING. 



A PROVERB of Northwest India declares that three 

 things make a man to be truly a man — to have a son 

 born to him, to dig a well, and to plant a tree. It is impos- 

 sible for the untraveled Englishman to realize the misery 

 of a treeless country. Europe has no natural deficiency 

 of trees; hence, bridge-building took the place of the old 

 Aryan tree-planting, as an act of piety to God, and of duty 

 to the future, in the counsels of the early Christian teach- 

 ers of the European nations. Both in East and West, trees 

 were no doubt the first temples, and the planting of groves 

 was the primitive form of church-building. Abraham we 

 are told, planted a grove in Beersheba, to commemorate 

 his solemn covenant; but among his descendants it became 

 in time the mark of a pious ruler to "cut down the groves," 

 as the seats of pagan worship : the mark of a careless ruler 

 to leave them untouched; and the mark of an impious ru- 

 ler to plant and dedicate new groves. It is not hard to find 

 reasons why the grove naturally became the first temple. 

 Men were no doubt impressed by the hoary age of trees 

 compared with the short life of man. A tree was often 

 the center around which each succeeding generation de- 

 posited its traditions — a visible bond uniting the departed 

 with the living, and the living with the unborn. The cool, 

 grateful shade of trees was a natural type of the gracious- 

 ness the worshipers sought for from the power they wor- 

 shipped — especially in Eastern lands, where shadow is so 

 precious and so exceptional. The yearly new birth and 

 death of their foilage was a national symbol of human 

 life. The darkness and densky of the grove, we must add, 

 hid the obscenities and cruelties which belonged to the 

 darker developments of heathen worship. 



Tree-planting has retained in Germany longer than else- 

 where something of its occult character, binding together 

 religion, nation, and family. In the Yosgessen, the old 

 German farmers were not allowed to marry until they had 

 done something for the future good of the tribe by plant- 

 ing a stated number of walnut-trees. 



The asking of a distinguished guest to plant a tree, is a 

 pleasant way of commemorating a visit. We do not 

 know that it is much used here. In 1852 the oratorian poet, 

 F. W. Faber, was visited at St. Mary's, Sydenham, by 

 Prince Massimo and Cardinal Wiseman, each of whom left 

 behind him the record of his visit in a tree of his own 

 planting. According to the German fandy, no tree planted 

 as a memorial will grow and flourieh unless it has a motto 

 given it at the time of its planting. 



In different parts of our country we may come across 

 trees — in Sherwood, indeed, across entire woods — planted 

 to commemorate national events. But our English tree- 

 plantings have long been mainly the work of individuals, 

 and not of communities. A tree planted in Lord Rollo's 

 garden at Duncrub, to commemorate the Union of Eng- 

 land and Scotland in 1707, a fir, eighty; feet high, and eight- 

 een feet in girth, was blown down in the gale of March, 

 1866. The greatest day of commemorative tree-planting 

 ever known in England was probably the first anniversary 

 of the Restoration, May 29th, 1661. The letters from dif- 

 ferent towns in the Mercurius Publicus and the King's Intel- 

 ligencer of that year, contain accounts of such plantings. 

 Many of these, however, were, like the Trees of Liberty, 

 planted only to last as long as the festival. In one letter 

 from Halesworth, in Suffolk, the ' ' own correspondent " 

 of the period writes: "The number of trees that were 

 planted in the town was so great that it perfectly resem- 

 bled an artificial forest. The whole town lay under so ab- 

 solute a disguise that the inhabitants knew not their own 

 houses." — {Mercurius Publicus, June 6, No. 23.) The 

 wholesale commemorative planting in the Sherwood dis- 

 trict marks victories gained by our famous admirals. 

 Lord Newark planted twenty-five acres, partly forest-tree 

 and partly fir, and called it Howe's Grove, in honor of Earl 

 Howe's great victory. A plantation of fifteen acres, ad- 

 joining Thoresby Park, is called after Earl St. Vincent; 

 and twelve acres on the north boundary of Budby Forest, 

 celebrate Lord Duncan. In other parts of the Sherwood 

 district great plantations bear the names of Nelson, St. Vin- 

 cent, Howe, and Spencer— the last in honor of the noble- 

 man who then presided at the admiralty, and to whose 

 judicious arrangement of the fleet the English successes 

 were in part attributed. — Chambers' Journal. 



Idttml H§intorfj. 



Loins XVI. A Crack Sportsman.— From the "Journal de 

 Louis XVI.," lately published by M. Nicolardot, it appears 

 that the unfortunate monarch was passionately fond of hunt- 

 ing. Louis XVI. , the meekest of mortals, was one of the 

 crack Nimrods. In his diary he records having brought 

 down 189,251 pieces, and 1,274 deer. When large game 

 was in abeyance, he would shoot martinets, squirrels, or 

 small game of any kind. Even swallows were not spared; 

 he averaged seventy a clay. An entry of the diary on the 

 28th July 1784, states, "killed 200 swallows." 



"BIRDS WALKING UNDER WATER" 

 * 



A LATE paragraph in this paper under the above head- 

 ing, concludes by requesting further observations on 

 the movements of birds under water. The writer assumes 

 that it would be "physically impossible" for a bird to swim 

 horizontally under water, "unless it could in some way as- 

 similate its specific gravity to that of the water around it." 



While it is perhaps not surprising that the ability of cer- 

 tain birds to progress under water in all directions should 

 not be generally known, owing to limited and infrequent 

 opportunities of observation, their possession of this power 

 is nevertheless established, and readily explained without 

 recourse to the above-mentioned theory. It is well known 

 to naturalists that cormorants, loons, grebes, and some al- 

 lied species habitually pursue their prey under water, some- 

 times at a depth of several fathoms. As their food consists 

 in large part of fish, they must be able to move rapidly in 

 any direction in order to secure it. I have only witnessed 

 the act myself under the most favorable circumstances of 

 observation, in the case of loons; but the mode of progres- 

 sion is essentially similar, if not the same, in other instan- 

 ces. From the stern of a steamer anchored in the quiet, 

 transparent water of the harbor of San Pedro, Southern 

 California, I once watched the movements of some loons 

 which were playing about the vessel without showing any 

 of the wildness these birds usually exhibit. They frequent- 

 ly swam and dived within a few feet of me, and in several 

 instances I could readily trace their course for some dis- 

 tar. ce under water. It was an interesting sight, and a novel 

 one, to see such wary birds disporting heedlessly just be- 

 low, gliding through the water with the ease and speed of a 

 fish, bespangled and glittering like fishes, too, with the 

 bubbles of air that clung to their sleek, glossy plumage. 

 They appeared to swim in every direction with equal facil- 

 ity, using both wings and legs. But it was not, in reality, 

 so much swimming as flying; the birds actually flew through 

 the water, moving the half-spread wings much as in ordi- 

 nary aerial flight. They appeared to shape their course 

 with strokes of the broad, webbed feet which projected, 

 rudderlike, far behind, and to propel themselves largely by 

 using the wings like fins; but as both members were in 

 continual motion the amount of impulse derived from each 

 source could not well be estimated. The birds sometimes 

 reached a depth at which they were lost to view, reappear- 

 ing nearly where they went down; and again, they accom- 

 plished the long distances they are well known to swim un- 

 der water in a horizontal direction, in both cases remaining 

 submerged for the same surprising length of time. It is not 

 in the least probable that they were prepared to swim in 

 this or that particular direction by a change in their spe- 

 cific gravity; it will be evident that no such alteration 

 would be required. 



As we all know, a bird dives by pushing itself down 

 with the feet or wings, or both, exactly as it swims on the 

 surface by pushing itself forward; in the former case over- 

 coming, by muscular exertion, its tendency to float, as well 

 as the simple resistance of the water to its progress. Now, 

 to swim horizontally under water the bird need only incline 

 the axis of the body obliquely downward at a certain slight 

 angle, and then push straight forward. For in this posi- 

 tion the bird opposes its broad flat back to the obliquely 

 downward action of the water, which offers the required 

 resistance to counteract the tendency to rise, as long as the 

 bird continues to propel itself onward. It could not re- 

 main under water motionless ; were its course arrested it 

 would immediately begin to rise obliquely backward. The 

 adjustment of the body at an angle which balances the up- 

 ward tendency with a resistance from above, is of course, 

 instinctively effected, and the direction is altered at will 

 by a change in the inclination of the body. Progress under 

 water is the resultant of three forces— muscular energy, 

 directed forward, specific gravity of the water acting verti- 

 cally upward, and an induced resistance of the water 

 pressing obliquely downward and backward. A certain 

 rate of speed is required to bring this last force into action, 

 much as "headway" is needed to make a vessel mind the 

 helm; if the motion slacken short of such rate the bird 

 would "make leeway" — that is, drift upward. The prin- 

 ciples involved are essentially the same as those upon which 

 a vessel sails up to the wind — the bird trims its boat-shaped 

 body to the water, just as the sails of a vessel are trimmed 

 to the wind. 



There is, however, no question that some birds possess 

 the power of altering their specific gravity decidedly— per- 

 haps to the extent of making themselves a little heavier 

 than the same bulk of water. Some of their performances 

 cannot, probably, be otherwise explained. When a grebe, 

 for instance, as is frequently witnessed, sinks back into the 

 water without perceptible move of its flippers, and with 

 scarcely a ripple, until only the head remains visible, the 

 bird has not dived in the ordinary sense of that term. It 

 has neither pulled nor pushed itself under, but just let it- 

 self down — sunk; and it is not evident how this could be 

 effected without some increase in specific gravity. On one 

 occasion I happened to see how a great change may be ef- 

 fected. It is simply a matter of a long breath. It is well known 

 that birds breathe air not only into their lungs, but also thence 

 into a system of inter-communicating cells in various parts 

 of the body, the amount thus inhaled and exhaled being, in 

 some cases at least, sufficient to effect the change in ques- 

 tion. Holding a wounded grebe in my hands I saw and 

 felt it swell with a long, labored inspiration that o seemed to 



