Some manufacturers are marketing limes of fair values under this designation, but the values change as the material changes. There are other manufacturers who are putting poor stuff on the market. Unless one knows the manufacturer and his processes, he should not pay a great deal for "agricultural lime." It is much better to buy a high-grade lime or limestone that is more nearly constant in composition. When the word "agricultural" is part of the brand, there is assurance that the percentage of waste stuff in it is relatively high. Unless one knows to the contrary, he should assume that a ton of finely pulverized limestone is worth more per ton than "agricultural lime." _Marl._ Marls vary in composition, as limestones do, but there are beds of chalky marl that contain very little clay and sand and are nearly a pure carbonate. It is only marls of high degree of purity that can be put on the market with profit, but beds of less pure marl furnish dressings for farms of the locality in many sections of the country. Some of these inferior marls have had so much clay and sand mixed with the lime carbonate that dressings must be heavy. The best lime marls provide excellent material for the correction of soil acidity, the actual value per ton being practically the same as that of the finest pulverized limestone. Some dealers in marl make extravagant claims for their goods, but any farmer may easily put these claims to the test and learn that he should not expect more than a fairly good carbonate of lime can do. Marl improves the physical condition of stiff soils only when used in large amount per acre, and this is true of any carbonate form, such as limestone. Little effect upon physical condition should be expected from the light application usually given when marl is purchased and transported some distance to the farm. The chalk marl on the market is used to correct soil acidity, and at the best it is worth only what good lime carbonate is worth. It has no hidden virtues, and cannot take the place of fertilizers. It is an excellent means of meeting the lime-requirement of land when bought right, and its fine division makes it distinctly superior to coarse stone. There should be no confusion of a lime marl with the so-called "green sand" marl. The latter is low in lime, and may be acid, the value of the marl being in a considerable percentage of plant food contained. _Oyster Shell._ Ground oyster shell is a good source of carbonate of lime. The percentage falls below that of limestone, but in addition there is a little nitrogen and phosphoric acid. An analysis of a good quality of oyster shell, as found on the market, will show 90% carbonate of lime. Burned oyster shell has something near the same composition as lime made from stone, but it goes back to hydrate and air-slaked forms rapidly. There is no large amount of burned shell lime on the market, the material known as shell lime being the ground shell, or lime carbonate.