Harvard School of Engineering and Applied Sciences

Oh, that's wonderful.

You are going to be a great engineer, and Harvard Engineering School is good, huh?

Well, you see, I-

I'm afraid we'll have to take her now.

Thus, South Africa will probably command a larger measure of interest and attention from the world henceforth than hitherto.

The Economic Aspects of Soil Erosion by Dr. N. S. Shaler, Professor of Geology in Harvard University and Dean of the Lawrence Scientific School.

as the scattered drops of a shower gather into streams the water begins to act in an erosive way if this gathering takes place at the height of five thousand feet above the sea each pound of the fluid has a store of energy of position which we term five thousand foot pounds which it is to expend on the path to the sea when the rain comes down on highlands the first stage of its journey to the sea is commonly made at high speed in torrents in the torrential division of a river system we always find the surface cast into steep sloped valleys generally the whole surface is composed of inclines ranging in declivity from five to thirty degrees or more on which surfaces the soil if it be present is always moving down the incline at a variable rate at times especially when softened by the frosts of winter and filled with water the earth on these steep hillsides slips in the manner of a landslide down to the bed of the stream there it for a short time blocks the way of the torrent but it is swiftly carried down to the river channels commonly the movement of these earth masses is in the manner of a glacier slow but steadfast amounting to a few lines or a few inches a year rarely to a foot or two in that length of time so general is this movement that although not readily noted without precise observations it may by accurate observations be determined on nearly all steep slopes which are covered with a thick layer of soil during the movement the expansion of the earth-water in times of frost the enlargement of the roots which penetrate the soil and in a measure the process of wetting and drying the detritus operates to thrust the mass the movement being in all cases in the direction in which gravity inclines it to go arriving at the margin of the torrent the procession of the detritus is cut away by the swiftly moving waters and sent on its way to the sea as above indicated this process of erosion by the slipping of the soil toward the torrent beds is characteristic of all steeply turned fields so long as the earth is covered by the normal forest growth the strong roots are likely to pass through the soil and fix themselves in the crevices of the underlying rocks and clamp so to speak the loose materials in their place in this way it comes about that one of the effects of deforesting a country even where the lesser vegetation is allowed to develop is to increase the rate at which the soil goes away to the streams as yet this country has not been long enough exposed to the destructive effects of tillage to afford striking instances of the effect of the reckless war which is waged upon the woods by the savages who play that they are the agents of civilization in europe examples of the irreparable damage which made thus be wrought abound perhaps the most striking are to be found in the apennines near florence where it is possible to walk for miles on mountain slopes without setting foot on anything but bare rock-fields which a century or so ago bore heavy forests nurtured in a fertile if not deep soil the last of the medicis who held these woods as crown lands cut the timber without any provision for the replacement of the trees with the result that the fine soil before it had time to obtain protection from plants was swept away in this manner a great area has been doomed to age-long sterility and a region made desolate which might with proper management have continued to be helpful to man for an unlimited period the mountainous countries of the old world with their vast reaches of bare rock slopes which down to recent centuries were forest-clad showed the destructive effects of man's heedless assault on the earth in this country there has not been time for this process of destruction by the axeman to manifest itself in a very serious way yet in the appalachians we can see the evil in rapid progress south of pennsylvania there is according to my reckoning based on observations in every state in that upland country an aggregate area of not less than three thousand square miles where the soil has been destroyed by the complete removal of the woods and the consequent passage of the earthy matter to the low lands and to the sea at the rate at which this process is now going on the loss in arable or forestable land may safely be reckoned at not less than one hundred square miles per annum in other words we are each year losing to the uses of man through unnecessary destruction a productive capacity which may be estimated as sufficient to sustain a population of a thousand people in considering the destruction which the elemental conditions bring upon a country which is subjected to the tax of civilization the most important fields to be noted are those of the highland districts for the reason that there the slopes are on the average steepest the rainfall is greatest and the action of frost is most considerable there the process of erosion is the most rapid and the results are the most irremediable there are however no lands in this country or in any other where the waste due to tillage is not noteworthy even in the prairies where the average declivity of the surface is not more than one or two degrees the effect of that bearing of the earth which is the necessary first step of tillage is to send a share of the earthy matter from the fields to the streams and thence to the seas the close observer who will walk for a day during a time of protracted rain along the banks of the main stream is likely to find that some of the tributaries carry water which is nearly clear while others discharge a very muddy flow examining the cause of the difference he will note that the relatively clear brooks come from fields that are not tilled being either in forest or grass while those which are very muddy have a large proportion of their area under plough culture while the destruction of a ploughed field in a given time is greater in proportion to the steepness of its slope there are practically no fields however slight their declivity which are not exposed in the same considerable measure to this kind of wasting in a degree it is the inevitable accompaniment of tillage which rests on the plan of expelling the natural growth of a soil that place may be made for artificially imposed vegetation however carefully the work may be done and whatever the nature of the crop the earth is for the time bared to the assaults of rain and wind the question may well be asked whether if this loss by erosion is a necessary element of tillage it is not certain that in time all the soils will go on their way to the sea and the earth thus be made unfit for the uses of man the answer to this is that the natural regimen of this soil provides a way by which a certain amount of waste in its mass may be in almost all cases made good through the decay of the underlying rocks this is accomplished by the action of that part of the rain-water which does not flow over the surface but finds its way into the soil and is slowly yielded to the streams in the form of distinct springs or more commonly in the broad sheet of water which flows down along the bed-rock or the hard pan until it enters the drainage channel of the area this underground water except in the rare places where caverns abound moves very slowly and has no erosive effect what material it takes away a relatively small amount is removed in solution penetrating to the bed-rock this water charged with carbonic dioxide and other compounds which add to its decay bringing effects attacks the bed-rocks breaks them up and with the assistance of the roots of the sturdier plants brings the hard stones into the state of soil in this way the natural waste derived from the solutions effected by the underground water the cutting along the streams and the slight wearing of the general surface by water action is compensated for by the steadfast reproduction of the soil at its base in the state of nature the rate of degradation of the earth's surface over a region such as the mississippi valley appears by the studies of humphreys and abbott to be not far from one foot in five thousand years at this rate of erosion we may from the field evidence presume that the underground decay will keep somewhat ahead of the wearing actions and so the soil rather gain than lose in depth under complete tillage such as is now applied the rate of downwearing will probably become as great as that which exists in the valley of the po where the surface descends at the rate of about one foot in a thousand years under these conditions we may be sure that the underground replacement of the soil cannot compensate for the wearing and that consequently the fertile layer will gradually disappear as it has done over large areas in the old world and is now doing in other fields of this country before proceeding to questions of a distinctly economic nature those which concern the steps which should be taken to arrest the wasting of our soils it will be well for us to consider the processes and rates of erosion on two of the many varieties of soils which plentifully exist in this country namely those of our glaciated districts and those found in the alluvial plains besides the true rivers

This is Rick Burgess from The Rick Burgess Show.

It's very difficult.

Last year I went to, I was in Harvard Business School in the Harvard School of Engineering.

I was at ClioCon.

I won, Dispute Buddy won a prize from Airwallex, the global growth grant.