THE FORCING POWER OF RAIN.

There is an old proverb which implies that England need never fear drought; and we have had clear evidence this year (1868) that an exceptionally dry summer is not necessarily followed by a bad harvest. But I believe that when a balance is carefully struck between the good and the evil effects resulting from excessive drought in England, it will be found that the latter largely prevail. In fact, it is only necessary to observe the effects which have followed the recent wet weather to recognise the fact that rain has a forcing power, the very diminished supply of which at the due season cannot fail to have seriously injurious effects. In various parts of England we see evidences of the action of such a power during the present autumn in the blossoming of trees, in the flowering of primroses¹ and other spring plants, in rich growths of fungi², and in various other ways. It cannot be doubted that there is here a comparative waste of powers which, expended³ in due season, would have produced valuable results.

The modern theories of the correlation⁴ of force suffice to show how enormous a loss a country suffers226 when there is a failure in the supply of rain, or when that supply comes out of its due season. When we consider rain in connection with the causes to which it is due, we begin to recognise the enormous amount of power of which the ordinary rainfall of a country is the representative; and we can well understand how it is that ‘the clouds drop fatness on the earth.’

The sun’s heat is, of course, the main agent—we may almost say the only agent—in supplying the rainfall of a country. The process of evaporation⁵ carried on over large portions of the ocean’s surface is continually storing up enormous masses of water in the form of invisible aqueous vapour, ready to be transformed into cloud, then wafted⁶ for hundreds of miles across seas and continents, to be finally precipitated⁷ over this or that country, according to the conditions which determine the downfall of rain. These processes do not appear, at first sight, indicative of any very great expenditure⁸ of force, yet in reality the force-equivalent of the rain-supply of England alone for a single year is something positively⁹ startling. It has been calculated that the amount of heat required to evaporate a quantity of water which would cover an area of 100 square miles to a depth of one inch would be equal to the heat which would be produced by the combustion¹⁰ of half a million tons of coals. The amount of force of which this consumption of heat would be the equivalent corresponds to that which would be required to raise a weight of upwards¹¹ of one thousand millions of tons to a height of one mile. Now, when we remember227 that the area of Great Britain and Ireland is about 120,000 square miles, and that the annual rainfall averages about 25 inches, we see that the force-equivalent of the rainfall is enormous. All the coal which could be raised from our English coal mines in hundreds of years would not give out heat enough to produce England’s rain-supply for a single year. When to this consideration we add the circumstance that the force of rain produces bad as well as good effects—the former when the rain falls at undue¹² seasons or in an irregular manner, the latter only when the rainfall is distributed in the usual manner among the seasons—we see that an important loss accrues¹³ to a country in such exceptional years as the present.

There are few subjects more interesting than those depending on the correlation of physical forces; and we may add that there are few the study of which bears more largely on questions of agricultural and commercial economy. It is only of late years that the silent forces of nature—forces continually in action, but which are too apt to pass unnoticed and unrecognised—have taken their due place in scientific inquiry¹⁴. Strangely enough, the subject has been found to have at once a most practical bearing on business relations, and an aspect more strikingly poetical¹⁵ than any other subject, perhaps, which men of science have ever taken in hand to investigate. We see the ordinary processes of Nature, as they are termed, taking their place in the workshop of modern wealth, and at the same time228 exhibited in a hundred striking and interesting physical relations. What, for instance, can be stranger or more poetical than the contrast which Professor Tyndall has instituted between that old friend of the agriculturist—the wintry snow-flake—and the wild scenery of the Alps? ‘I have seen,’ he says, ‘the wild stone-avalanches of the Alps, which smoke and thunder down the declivities with a vehemence¹⁶ almost sufficient to stun¹⁷ the observer. I have also seen snow-flakes descending¹⁸ so softly as not to hurt the fragile spangles of which they were composed; yet to produce from aqueous vapour a quantity which a child could carry of that tender material demands an exertion¹⁹ of energy competent to gather up the shattered blocks of the largest stone-avalanche I have ever seen, and pitch them to twice the height from which they fell.’

I may point out in this place the important connection which exists between the rainfall of a country and the amount of forest land. I notice that in parts of America attention is being paid—with markedly good results—to the influence of forests in encouraging rainfall. We have here an instance in which cause and effect are interchangeable. Rain encourages the growth of an abundant vegetation, and abundant vegetation in turn tends to produce a state of the superincumbent atmosphere which encourages the precipitation of rain. The consequence is, that it is very necessary to check, before it is too late, the processes which lead to the gradual destruction of forests. If these processes are continued until the climate has229 become excessively dry, it is almost impossible to remedy the mischief²⁰, simply because the want of moisture is destructive to the trees which may be planted to encourage rainfall. Thus there are few processes more difficult (as has been found by experience in parts of Spain and elsewhere) than the change of an arid²¹ region into a vegetation-covered district. In fact, if the region is one of great extent, the attempt to effect such a change is a perfectly²² hopeless one. On the other hand, the contrary process—that is, the attempt to change a climate which is too moist into one of less humidity—is in general not attended with much difficulty. A judicious²³ system of clearing nearly always leads to the desired result.

The dryness of the past year has not been due to the want of moisture in the air, nor to the exceptionally unclouded condition of our skies. I believe that, on the whole, the skies have been rather more cloudy than usual this year. The fact that so little dew has fallen is a sufficient proof that the nights have been on the whole more cloudy than usual, since, as is well known, the presence of clouds, by checking the radiation of the earth’s heat, prevents (or at least diminishes) the formation of dew. The fact would seem to be that the westerly and south-westerly winds which usually blow over England during a considerable part of the year, bringing with them large quantities of aqueous vapour from above the great Gulf²⁴ Stream, have this year blown somewhat higher than usual. Why this should be it is not very easy to say. The height of230 the vapour-laden winds is usually supposed to depend on the heat of the weather. In summer, for instance, the clouds range higher, and therefore travel farther inland before they fall in rain. In winter, on the contrary, they travel low, and hence the rain falls more freely in the western than in the eastern counties during winter. A similar relation prevails in the Scandinavian peninsula—Norway receiving more rain in winter than in summer, while Sweden receives more rain in summer than in winter. But this summer the rain-clouds have blown so much higher than usual as to pass beyond England altogether. Possibly we may find an explanation in the fact that before reaching our shores at all the clouds were relieved by heavy rainfalls—probably due to some exceptional electrical relations—over parts of the Atlantic Ocean. It is stated that the steam-ships from America this summer were, in many instances, drenched²⁵ by heavy showers until they neared the coasts of England.

(From the Daily News, October 5, 1868.)

1 primroses   

n.报春花( primrose的名词复数 )；淡黄色；追求享乐（招至恶果）

参考例句：

• Wild flowers such as orchids and primroses are becoming rare. 兰花和报春花这类野花越来越稀少了。 来自《简明英汉词典》
• The primroses were bollming; spring was in evidence. 迎春花开了，春天显然已经到了。 来自互联网

2 fungi   

n.真菌，霉菌

参考例句：

• Students practice to apply the study of genetics to multicellular plants and fungi.学生们练习把基因学应用到多细胞植物和真菌中。
• The lawn was covered with fungi.草地上到处都是蘑菇。

3 expended   

v.花费( expend的过去式和过去分词 )；使用（钱等）做某事；用光；耗尽

参考例句：

• She expended all her efforts on the care of home and children. 她把所有精力都花在料理家务和照顾孩子上。
• The enemy had expended all their ammunition. 敌人已耗尽所有的弹药。 来自《简明英汉词典》

4 correlation   

n.相互关系，相关，关连

参考例句：

• The second group of measurements had a high correlation with the first.第二组测量数据与第一组高度相关。
• A high correlation exists in America between education and economic position.教育和经济地位在美国有极密切的关系。

5 evaporation   

n.蒸发，消失

参考例句：

• Be careful not to lose too much liquid by evaporation.小心不要因蒸发失去太多水分。
• Our bodies can sweat,thereby losing heat by evaporation.我们的身体能出汗，由此可以蒸发散热。

6 wafted   

v.吹送，飘送，（使）浮动( waft的过去式和过去分词 )

参考例句：

• The sound of their voices wafted across the lake. 他们的声音飘过湖面传到了另一边。
• A delicious smell of freshly baked bread wafted across the garden. 花园中飘过一股刚出炉面包的香味。 来自《简明英汉词典》

7 precipitated   

v.（突如其来地）使发生( precipitate的过去式和过去分词 )；促成；猛然摔下；使沉淀

参考例句：

• His resignation precipitated a leadership crisis. 他的辞职立即引发了领导层的危机。
• He lost his footing and was precipitated to the ground. 他失足摔倒在地上。 来自《简明英汉词典》

8 expenditure   

n.(时间、劳力、金钱等)支出；使用，消耗

参考例句：

• The entry of all expenditure is necessary.有必要把一切开支入账。
• The monthly expenditure of our family is four hundred dollars altogether.我们一家的开销每月共计四百元。

9 positively   

adv.明确地，断然，坚决地；实在，确实

参考例句：

• She was positively glowing with happiness.她满脸幸福。
• The weather was positively poisonous.这天气着实讨厌。

10 combustion   

n.燃烧；氧化；骚动

参考例句：

• We might be tempted to think of combustion.我们也许会联想到氧化。
• The smoke formed by their combustion is negligible.由它燃烧所生成的烟是可忽略的。

11 upwards   

adv.向上，在更高处...以上

参考例句：

• The trend of prices is still upwards.物价的趋向是仍在上涨。
• The smoke rose straight upwards.烟一直向上升。

12 undue   

adj.过分的；不适当的；未到期的

参考例句：

• Don't treat the matter with undue haste.不要过急地处理此事。
• It would be wise not to give undue importance to his criticisms.最好不要过分看重他的批评。

13 accrues   

v.增加( accrue的第三人称单数 )；（通过自然增长）产生；获得；（使钱款、债务）积累

参考例句：

• If you put money in the bank, interest accrues. 如你将钱存于银行，则自然生息。 来自《现代英汉综合大词典》
• Interest accrues on a bank accout. 银行账户的利息在增长。 来自《简明英汉词典》

14 inquiry   

n.打听，询问，调查，查问

参考例句：

• Many parents have been pressing for an inquiry into the problem.许多家长迫切要求调查这个问题。
• The field of inquiry has narrowed down to five persons.调查的范围已经缩小到只剩5个人了。

15 poetical   

adj.似诗人的；诗一般的；韵文的；富有诗意的

参考例句：

• This is a poetical picture of the landscape. 这是一幅富有诗意的风景画。 来自《简明英汉词典》
• John is making a periphrastic study in a worn-out poetical fashion. 约翰正在对陈腐的诗风做迂回冗长的研究。 来自辞典例句

16 vehemence   

n.热切；激烈；愤怒

参考例句：

• The attack increased in vehemence.进攻越来越猛烈。
• She was astonished at his vehemence.她对他的激昂感到惊讶。

17 stun   

vt.打昏，使昏迷，使震惊，使惊叹

参考例句：

• When they told me she had gone missing I was totally stunned.他们告诉我她不见了时，我当时完全惊呆了。
• Sam stood his ground and got a blow that stunned him.萨姆站在原地，被一下打昏了。

18 descending   

n. 下行 adj. 下降的

参考例句：

• The results are expressed in descending numerical order . 结果按数字降序列出。
• The climbers stopped to orient themselves before descending the mountain. 登山者先停下来确定所在的位置，然后再下山。

19 exertion   

n.尽力，努力

参考例句：

• We were sweating profusely from the exertion of moving the furniture.我们搬动家具大费气力，累得大汗淋漓。
• She was hot and breathless from the exertion of cycling uphill.由于用力骑车爬坡，她浑身发热。

20 mischief   

n.损害，伤害，危害；恶作剧，捣蛋，胡闹

参考例句：

• Nobody took notice of the mischief of the matter. 没有人注意到这件事情所带来的危害。
• He seems to intend mischief.看来他想捣蛋。

21 arid   

adj.干旱的；(土地)贫瘠的

参考例句：

• These trees will shield off arid winds and protect the fields.这些树能挡住旱风,保护农田。
• There are serious problems of land degradation in some arid zones.在一些干旱地带存在严重的土地退化问题。

22 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

23 judicious   

adj.明智的，明断的，能作出明智决定的

参考例句：

• We should listen to the judicious opinion of that old man.我们应该听取那位老人明智的意见。
• A judicious parent encourages his children to make their own decisions.贤明的父亲鼓励儿女自作抉择。

24 gulf   

n.海湾；深渊，鸿沟；分歧，隔阂

参考例句：

• The gulf between the two leaders cannot be bridged.两位领导人之间的鸿沟难以跨越。
• There is a gulf between the two cities.这两座城市间有个海湾。

25 drenched   

adj.湿透的；充满的v.使湿透( drench的过去式和过去分词 )；在某人（某物）上大量使用（某液体）

参考例句：

• We were caught in the storm and got drenched to the skin. 我们遇上了暴雨，淋得浑身透湿。
• The rain drenched us. 雨把我们淋得湿透。 来自《简明英汉词典》