A good rotation will include both chemical and mechanical differences, and place tap-roots in a course between surface roots, as, for example, Carrot, Parsnip, and Beet, after Cabbage, Cauliflower, and Broccoli; and light, quick surface crops, such as Spinach, to serve as substitutes for fallows.  The cropping of the kitchen garden should be, as far as possible, so ordered that plants of the same natural families never immediately succeed one another; and, above all things, it is important to shift from place to place, year after year, the Cabbages and the Potatoes, because these are the most exhaustive crops we grow.  In a ton of Potatoes there are about twelve pounds of potash, four pounds of sulphuric acid, four pounds of phosphoric acid, and one pound of magnesia.  We may replace these substances by abundant manuring, and we are bound to say that the best rotation will not obviate the necessity for manuring; but even then it is well to crop the plot with Peas, Spinach, Lettuce, and other plants that occupy it for a comparatively brief space of time, and necessitate much digging and stirring; for these mechanical agencies combine with the manure in preparing the plot to grow Potatoes again much better than if the land were kept to this crop only from year to year.  If we could mark out a plot of ground into four parts, we should devote one plot to permanent crops—­such as Asparagus, Sea Kale, and Rhubarb—­and on the other three keep the crops revolving in some such order as this:  No. 1, Potatoes, Celery, Leek, Carrot, Parsnip, Beet, &c.  No. 2, Peas, Beans, Onions, Summer Spinach, &c., followed by Turnips for winter use, Cabbage for spring use, and Winter Spinach.  No. 3, Brassicas, including Broccoli, Brussels Sprouts, Kale, &c.  In the following year the original No. 1 would be cropped as No. 2, and No. 2 as No. 3.  In the third season corresponding changes would be made, constituting a three-course system.  The cultivator must use discretion in cropping vacant ground.  As an example it will be obvious that land cleared of Early Potatoes will be very suitable for planting Strawberries.  Another point is worth attention:  Peas sown on the lines where Celery has been grown will thrive without any preparation beyond levelling the ground and drawing the necessary drills.  This is a West of England custom, and it answers exceedingly well.

THE CHEMISTRY OF GARDEN CROPS

A Consideration of the chemistry of the crops that engage attention in this country will afford an explanation of one great difference between farming and gardening.  And this difference should be kept in mind by all classes of cultivators as the basis of operations in tillage, cropping, and the order and character of rotations.  The first thing to discover in the cropping of a farm is the kind of vegetation for which the land is best adapted to insure, in a run of seasons, fairly profitable results.  If the soil is unfit