cuttings of the hedges, covered with straw. In Leicestershire nearly a century ago, and perhaps earlier, a conduit was formed in clay at the bottom of the drain by a superimposed turf (locally called clod-soughing); and the practice is not quite exploded in that and other counties, which are backward in their agriculture. Attempts, moreover, were made in various parts of England to form a conduit by means of a mole-plough. This instrument had a great but very transient reputation. Smith of Deanston was therefore by no means the author of thorough-draining, but he saw much more clearly than any of his predecessors the benefits to be derived from it, and he has the high merit of having brought them prominently before the public. No doubt whatever can exist that Mr. Smith gave the first effectual impulse to the practice, and to that extent his name is justly associated with thorough-draining. One sentence in an article which he furnished to "The Third Report of Drummond's Agricultural Museum," makes a considerable approach to a right conception of the advantages of thorough-draining, as they are now revealed

to us.

"When soil is immediately incumbent on open rock, especially on whin or green-stone, which is very open from its many fissures, the land is always uniformly fertile. If, therefore, we observe carefully the operations of nature, we shall never be at a loss for principles to guide us in the cultivation of the soil. In the last stated example, the open rock under the soil affords frequent and pretty uniform channels of escape for the water; hence the obvious suggestion of the frequent drain system.”

So utterly innocent was poor Johnstone of any such ideas, that in a chapter on "Hollow-draining in General," he publishes such stuff as follows:

“In soils that are so tenacious as to retain water on the surface till evaporation carries it off, such as are found in Sussex, Surrey, and in many other counties, this method of draining has been tried, and found entirely to fail."

"Open trenches, with the ridges and waterfurrows properly formed and directed, is the only method whereby its drainage can be effectually accomplished. It is necessary to lay it up in ridges properly placed, and to cut small open drains across the ridges where requisite, communicating with each other, and with the furrows; and thus all the water-furrows operate as drains "—a singular conception, certainly, of an art on which he published a book in quarto. Smith's execution was inferior both to his conception and to his zeal. The depth of hist frequent drains was not sufficient to attain even the benefits which he foresaw; the materials for his conduit were cumbrous. The quantity of surplus left after refilling, when 15 in. of stone are put into a drain several inches wide at bottom, is very objectionable; and his prices for the execution of the work, when transferred to England, are fabulous. He has the merit of having first stated boldly that all drained lands should be worked flat without ridge or furrow, and he prescribes the line of steepest descent for the general direction of drains, and gives correctly some of the reasons for that practice. If his powers of reasoning had been equal to his zeal, or even to his perception, he would not have allowed himself to be outstripped, as he has been, by others in an art which he had in some degree made his own.

Josiah Parkes, C.E., in a work entitled "Essays on the Philosophy and Art of Land-drainage," published last year,* has very materially extended the objects and benefits of thorough-draining, and for every extension has given authentic instances and philosophical reasons. Mr. Parkes's style is clear and unaffected, and we think that very few holes can be picked in his reasoning. His first Essay is entitled, 'On the Influence of Water on the Temperature of Soils;" also, "On the Quantity of Rain-water and its Discharge by Drains." It is the first attempt which we have seen to reduce

*The former of these Essays had appeared in the Journal of the Agricultural Society in 1844, and the latter in 1846.

draining to a science; and, where want of data forbids that object to be obtained, Mr. Parkes indicates very clearly the avenues to future success. The treatise is somewhat too scientific for general agricultural readers, and on that account not fitted to be transferred in the form of a connected abstract into our pages; but it contains several interesting tables, and is pregnant with important facts and accurate deductions, of which we shall avail ourselves, without further acknowledgment, in the remarks on thorough-draining which we propose to offer to our readers. Mr. Parkes's second Essay, the Newcastle Lecture, to which we have already referred, is more popular in its nature, and very practical. Every farmer may read it with advantage. Mr. Mechi has given us "Experience in Drainage." He is an experimentalist in agriculture, and we should think a very sanguine one. With respect to many of his speculative conclusions, we should be sorry to give a directly adverse opinion; but we fear that, in order to escape doing so, we must take refuge in the modified Scotch verdict-not proven. We could not speak harshly of a gentleman whose assistance we crave at our toilet every morning, who imparts so freely to the public his failures as well as his successes, and who appears to bear so good-humouredly the banterings of the London Farmers' Club and the "Mark Lane Express." Moreover, Mr. Mechi asks very acute questions, and makes shrewd re_marks, some of which we may not improbably call to our

aid.

Here we take our leave of draining literature, and descend to practice. We will assume, without proving, that water of drainage, stagnating in the soil, is prejudicial to esculent vegetation. If this be not so, all that we and our predecessors have learnt and written, has been learnt and written in vain. We will assume, also, that to raise the temperature of what are familiarly and justly called our cold soils, will be beneficial to vegetation. Having made. these assumptions, we will prove 1st, that the main

cause of the coldness of these soils is the removal of the water of drainage by evaporation; 2ndly, that their temperature is very much raised during the vegetative season of the year by the removal of this water by efficient drainage; 3rdly, we will state the reasons for our conviction that, in all soils, the existence of the water-table within less than 4 feet of the surface of the land is prejudicial to vegetation; 4thly, we will show that the water of drainage will be best removed at a reasonable expense, and the level of the water-table will be best reduced by frequent parallel drains of a depth never less than 4 feet; 5thly, that the direction of these drains should, as a general rule, be in the line of steepest descent; 6thly, that pipes and collars form a better and cheaper conduit than any other which has been hitherto adopted; and, 7thly, we will give our opinion on the disputed point whether, in the most retentive soils, drains of 4 feet will effectually remove the water of drainage.

1st. The main cause of the coldness of retentive soils is the removal of water of drainage by evaporation.

The evaporation of water produces cold: it cools wine; in hot climates it produces ice. These facts are known to every one. To determine the actual degree of cold produced by the evaporation of one pound of water from soil is rather a complicated, and not a very certain, operation; but scientific reasons are given for an approximation to this result that the evaporation of one pound of water lowers the temperature of 100 lbs. of soil 10°. That is to say, that if to 100 lbs. of soil holding all the water which it can by attraction, but containing no water of drainage, is added one pound of water which it has no means of discharging except by evaporation, it will, by the time that it has so discharged it, be 10° colder than it would have been if it had the power of discharging this 1 lb. by filtration; or, more practically, that if rain, entering in the proportion of 1 lb. to 100 lbs. into a retentive soil which is saturated with water of attraction, is discharged by evaporation,

it lowers the temperature of that soil 10°. If the soil has the means of discharging that 1 lb. of water by filtration, no effect is produced beyond what is due to the relative temperatures of the rain and of the soil. Mr. Dickenson, the eminent paper-maker, who has several mills and a considerable landed estate in Hertfordshire, has deduced from a series of observations, which are, we believe, entitled to great confidence, that of an annual fall of 26 inches of rain, about 11 are filtered through a porous soil. The whole of this 11 inches (and probably more) must be got rid of by a retentive soil, either by evaporation or by superficial discharge. The proportions in which each of these means will operate will vary in every case, but this will be an universal feature, that these 11 inches will maintain in undrained retentive soils, at all except some accidental periods of excessive drought, a permanent supply of water of drainage, which will be in constant course of evaporation, and will constantly produce the cold consequent thereon. Retentive soils never can be so warm as porous, for a simple reason. Every one knows, or may know, that if into two flower-pots, with holes in the bottom, are put respectively equal portions of gravel and clay, equally heated to any point short of torrefaction, and if equal quantities of water are administered to the surface of each, water (water of drainage) will run from the gravel long before it begins to run from the clay. Gravel can hold by attraction much less water than clay can. At the time when each is saturated by water of attraction, and neither holds any water of drainage, evaporation will begin to act upon the water in each, and will act most strongly in the vegetative period of the year. The cold produced will be in proportion to the quantities of water evaporated respectively, and will of course be greatest in the retentive soil. We will reserve a further cause of coolness in retentive soils, which is also connected with evaporation, till we have spoken of the depths of drains.

2nd. The temperature of retentive soils is very much