March 1, 1902.] THE TROPICAL AGRICULTURIST. 593 
disasters. During tiie first half of the century the 
United -State of America forgot or disregarded all 
this, and destroyed thoir primeval forests at a whole- 
sale rate. They have now seen with their own eyea 
ho-« their former steady (and regular streams have 
become transformed into torrents, raging down so 
long as it rains, and dry for the rest of the jear. 
The matter is proved beyond dispute. " Thus where- 
ver man has to fear floods, he should plant forests 
as his best of all protections. They will give him 
important other advantages into the bargain as already 
shown. 
The figures given above refer to large basins where 
the slopes ax'e partly bare, partly cultivated, and 
partly forests or grass. Figures relating to basins 
of one kind exclusively would be of value. Since 
1S60, M.M. Jeandei, Cantegril, and Bellaud have 
been makii g comparisons between neighbouring basins, 
and they find the tendency to floods to be diminished 
by one-half in the wooded basins. Their work is 
not perfect, but it is the best available, the researches 
of M. Belgiand being worthless on account of de- 
fective conditions. The Swiss Forest Research Station 
is now beginning experiments in this direction in 
two adjoining basins, one wooded, the other almost 
without wood. iVlany rain-gauges will give the true 
rainfall, and the outflow will be measured in the 
streams v?ith precision by means of weirs. 
The quantity saved from .flowing away on the 
surface can be estimated from the springs, but only 
approximately. There are many instances of springs 
drying up or decreasing in quantity and regularity 
through the clearing of their basins, as also of 
springs being brought to life again by the growth of 
forests. There are lists of these in specialist publi- 
cations, but a few more may here be cited, because 
they are recent, perhaps little known, and warranted 
by competent observers. M. Crahay, Inspector of 
Forests at Brussels, in 1698, qdoted instances of the 
sources of the Sure at Planchimont, &o-: — 
" Since the spruce plantation of S5 years back, the 
flow has become more regular. One which used to 
be dry all the summer is now never dry, and is now 
about 220 feet higher up than it used to be. At 
Bois le Francais, in the commune of Villersdovant- 
Orval, after the clearance of an old copice with 
standards, two springs dried up. The place where 
the water came ont> and the little bed it ran in, are still 
to be seen. " 
At the international Congress of Sylviculture, held 
at Paris in 1900, M. Servier, a landowner at Lamure 
sur Azergues (Rhone), made an interesting commu- 
nication "On the hydrostatic phenomena following 
the planting of conifers." The soil is sandy. It was, 
till recently, almost devoid of wood, a fact ten- 
ding towards floods and torrents. Wherever a small 
clump of wood remained, the spot was generally 
marked by a spring. There ia a spring on the 
western edge of one of these clumps. Every time 
the coppice is felled the spring diminishes, and as 
the coppice grows, the spring recovers its volume. 
M. Bargmann quotes two springs in the communal 
forest of Storkensohn (vallej'- of Saint Amarin, near 
Urbes) which dried up when the forest above it was 
felled, but a new spring appeared about 500 Jcet 
loiuer altitude where no fellings had been made. " It 
ia easy to see that the disappearance of forest 
completely changes the conditions of evaporation and 
surface flow. Both are increased by diaforestment. " 
The only conclusion possible is, that the moisture 
lost by increased evuporation and quicker surface 
flow is much greater than the gain by cessation of 
root-suction. 
It was mentioned just now that the portion saved 
from surface flow could only be roiighlij estimated 
from the springs. This is because all the water 
saved does not reappear in springs. Some of it goes 
as deep aa 1,500 to 3,000 feet to form subterranean 
reservoirs which are available for artesian wells ; for 
instance, the artesian wells pf Paris, the supply for 
^iiich eink^ io aloog th§ otitcrop of tb^ gKeeugaucI 
in the basin of the Meuse. Elsewhere the water 
may sink in till it fiuds an outlet into some ocean. 
In some cases, the subterranean water losing its 
outlet in one basin may work across to another 
valley altogether, and increase the springs there. 
Finally, and most important, the soil itself must 
be considered as a great sponge, the degree of 
saturation of which varies irregularly according to 
the abundance and persistence of the rains. If a year 
begins with a low level of saturation and subterranean 
waters, and ends with a higher level or degree of 
saturation, it is evident that the surface flow of that 
year must have been less than normal, much of 
the normal surface flow having been absorbed to 
the benefit of the subterranean supply. Hence, the 
relation between the actual rainfall and the surface 
flow in that year will be distrubed, being less than 
would have been the case if the year had begun 
with full resources. In the one case the relation 
will be less than the average, in the other case 
more. In the one case the budget begins with an over- 
draft which has to be met, in the other there has 
been something " brought over." 
As the subterranean waters are beyond the reach 
of all raeasurement, it can only be juoged that when 
the springs run full,, the soil is full, and when the 
springs diminish, the subterranean reserves are low. 
So long as the springs remain normal, there is 
equilibrium. The time elapsing between the dis- 
appearance of the water underground and its re-ap- 
pearance in the springs is very variable. In coarae 
or Assured soils the springs begin visibly to iucreaaa 
almost as soon aa the rain begins. In very com- 
pact soils, and when the distance of infiltration is 
long, the process lasts for years. In the first class 
of cases just mentioned there may be damage. On 
steep slopes and in soft loose soils the streams iig 
deep beds and cut away banks whose removal causes 
landslips. Good earth ia continually being carried 
away and raw mineral soil exposed. Needless to 
dilate further on this point. Here, again, the forest 
is the natural remedy. Across all these little streams 
living weirs are constructed. These are formed of 
willow cuttings which scon strike root and produce 
vigorous shoots. .A. stout fence ia thus prodnceeU which 
rises as the river bed itself risea, forming a filter 
through which all the water indeed passes, but its 
evil impetuosity ia ended. In torrent beds of great 
width trees are planted, such is the alder forest 
which is so jealously maintained in the bed of the 
Veneon, where it joins the Romanche. The 
forest checks the violence of the flow, and compels 
the deposit of sediment which would otherwise go 
further down and raise still more the already too 
elevated bed of the Romanche ; these are the best 
kinds of dams, they cost little to construct and 
nothing for maintenance. The method is not always 
available. But it is not adopted nearly so often as it 
might be. It ia only ihrough the action of forests 
that the rivers arrive at the sea in a steady and 
respectable manner, having throughout their courses 
rendered the highest possible aervices to man, to 
animals and to plants, by springs, by percolation, 
by irrigation, by furnishing power, by providing the 
means of transport, &c, — Indian Forester, 
F, Gleadow. 
SISAL HEMP AGAIN. 
It is as yet too soon to obtain a report of restslid 
from the Sisal hemp-growers who last year obtained 
parcels of plants from the Department of Agricul- 
ture, as it takes at least three years before the plants 
are old enough to yield thetiist crop of leaves. We 
have advocated the growing of this valuable fibre, 
for the reason that poor laud not adapted for cereal 
or root crops can be utilised profitably at very small 
expense. Some have hesitated to plant, owing to 
the fear that esgensivo machiusjcy woiUii be needed 
