As this question, "how am I to renovate my old garden?" is invariably put by a numerous class of your readers - wh^perhaps cannot afford to employ a professional gardener, and are therefore obliged to look to the "Horticulturist" for information on all gnrden-ing matters - the following remarks are respectfully submitcd for their perusal. The remedy I am about to propose is not a new one, for as I consider the radical cure the best for all kinds of disease, I at once prescribe trenching. As the class of readers to which I allude may not be acquainted with the modus operandi, I will proceed to lay my method before them - which from long experience, I have known to be effectual.

We will suppose a square of ground in the garden, bounded by walks east, west, north and south, and we will commence at the west side and trench towards the east. The first thing to be done, is to open a trench two and and a half feet wide, and two feet deep, on the west side, running from north to south - throw the earth from this trench in a pile along the west side of it - the practice of many in wheeling this opening over to the east side, where they are to finish, I always considered nearly one-third of the whole labor. As soon as the first trench is shoveled out clean, to the depth of two feet, (I vary the depth according to the nature of the subsoil, i. e., if good sandy loam I go deeper, if very gravelly, not so deep, say eighteen or twenty inches,) I commence by placing a layer of dung along the bottom of the trench - at the rate of on; large barrow load to every fifteen feet of the trench. I then mark with a line, another trench at the east side of this, two and a half feet wide also, and having one of "Ames' spades," No. 2,I proceed to dig the top of this trench and throw it on the dung which is placed on the bottom of the first; in digging, I put the spade down its full length, and proceed until I have the entire surface soil of the second trench on the bottom of the first.

There will be a quantity of loose earth after this spading - before I shovel this in, I spread another coat of manure on top of the earth I have just thrown in, and then shovel the loose earth on top of it. I now commence to dig the bottom of the second trench, throwing it also on to the first, and shovel out the loose earth that falls from my spade, leaving the bottom of the trench level and clean. I have now the first trench finished, and proceed on toward the cast the same way - lining off every trench until I come within four of the end; I then commence making each of my trenches about five inches narrower than the preceding one - the object of this is to bring it gradually to a close - the last trench being about fifteen inches wide. Having placed the manure at the bottom of the last trench, as before directed, I now commence leveling back, and bringing the whole piece to a grade. In this process let the spade down as deep as possible, in order to mix the old soil and the new, thoroughly- - I keep it well from me, remembering that I have a pile of earth at the west side, that has got to be worked in.

The chief advantage that I claim for this method, (which has no claim to ori-nality,)is the chance it gives me of having a good opening where I finish, of giving the soil a thorough mixing - another is, I can spade the whole piece over in half the time it would take me to wheel the opening surplus over to the east side. I would here suggest, if the sub-soil is not too hard, it would be the most perfect mode, to spade the first coat of manure into the bottom of the trench, which would loosen the soil eight or ten inches more. I trenched an asparagus bed in this style for Messrs. Parsons', of Flushing, six years ago - here I could not practice it, the subsoil being too hard.

After the piece is leveled, I put on a good top-dressing of manure; and the best crops to plant the first year would be potatoes, cabbage or cauliflower, anything in fact, that requires a good deal of hoeing. October and November is the best time to trench - you have more leisure then; the ground is more easily worked; you can put all your melon vines, carrot, parsnep, turnep, and beet tops, leaves, etc, in the bottom of your trenches. As soon as the frost is out of the ground in the spring, is the next best time. Ground that has been trenched, will, in eight or ten years, become black by the annual application of manures - trench this over again and it will improve it. It is a great mistake for any one to suppose he can renovate an old garden, by piling on it annually, a quantity of barnyard manure - if he will not trench, he must try a rotation of manures, say lime one year, guano another, or better still, a good coat of yellow loam from an old pasture. Trenching is the radical cure, as it creates a deep soil. Old mother earth will assuredly turn up her nose at being drugged with one kind of manure all the time, as she invariably does, at producing the same crop for a succession of years, on the same space.

A rotation of manures, and a rotation of crops, are in my opinion, governed by the same laws. Occasionally I see a correspondent in your Journal who has got sick of using stable manure, resort to Guano, bone-dust, spent tan, etc, and finding beneficial results arise therefrom, immediately sings the praises of guano, spent tan, etc, and their superiority over stable manure - so overjoyed is he, that he thinks he has discovered the philosopher's stone. My opinion is, that his success proceeds more from having employed a new agent, than to any intrinsic virtues that either the guano or tan-berk possess over stable manure, which if followed up for any length of time, would soon demonstrate the necessity of a change. I therefore look upon a deep, well trenched soil, as the great ameliorator. A rotation of crops, and a rotation of manures, and mulching, I advocate as much as trenching; and tan-bark is the very best material for the latter purpose, which is all it is good for. I should be very hard pushed when I should mix it with the soil, notwithstanding that Mr. Cleveland's grape vine found their way into it.

They were attracted there by the moisture which the tan holds; the roots were evidently near the surface, and a pile of sawdust, or leaves, or any non-conductor of heat, would produce the same results. I fear I have trespassed too long on your valuable space - but as Irishmen sometimes have a roundabout method of conveying their ideas, I lay claim to every indulgence that is extended to them on that head. I am sir, yours respectfully, Jonx Quinn.

Ida Farm, Troy, December 17, 1350