properly adjusted lens of glass in front of the eye. This, of course, is absolutely without the power of accommodation, and different glasses have to be used for seeing at different distances. Professor Helmholtz adopts the conclusion that the perfection of the eye depends not upon the excellence of its construction as an optical instrument, but upon the manner in which it is used. The chromatic aberration of its humors, the astigmatism of its irregular contours, the blind-gaps of its nerve-screen, the imperfect transparency of its refractive media, the interposition of blood-vessels in front of the retinal membrane, the narrow limitation of the area of sharp definition, and the prevalent blurring of the lateral parts of the field, are all conditions that must be classed as optical imperfections. Yet every one of these imperfections is so counteracted and neutralized in the use of the organ under the plan of the employment of two eyes, and under the expedient of the rapid transference of the attention to different parts of the image, that it is actually unrecognized as a defect, and undiscovered until the most refined powers of scientific investigation have been brought to bear for its detection.

There are many injuries to which the eye is subject, and many conditions having an important bearing on the preservation of good eyesight, besides those mentioned in connection with structural or induced defects of form. It is Mr. Carter's belief that a very large proportion of what is generally regarded as congenital blindness is really caused after birth by ignorant or careless treatment. He puts the proportion as high as ninety-nine cases in one hundred. The eyes of new-born infants are doubtless extremely sensitive to the effects of light and temperature, and are imperfectly shielded by nature. "From the imperfect development of the bones of the infant skull," says Mr. Carter, "the eyes are placed, so to speak, on the surface, instead of being in hollows; the eyebrows and eyelashes are short, thin, and pale; the eyelids are almost transparent, and the irides are imperfectly furnished

FALKLAND ISLANDS. These islands form a group in the South Atlantic Ocean, about two hundred and fifty miles northeast of Tierra del Fuego. The number of islands is about two hundred, but only two of them are of any considerable size. Their whole superficies is reckoned at 5,000,000 acres. A few years ago penguins and sea-lions chiefly occupied their shores; but of late the English Government has encouraged emigration to them, and now numberless sheep fatten on their grass. These yield to their owners such an abundance of wool that it has become an article of exportation growing yearly in impor

with opaque pigment. In the first weeks of life, moreover, infants are unable to shelter themselves from dazzling light by changing the position of the head." Protection from too strong light and from sudden or violent changes either of light or temperature, proper attention to cleanliness and ventilation, and the intelligent treatment of purulent ophthalmia when it shows itself, would in his opinion prevent a very large proportion of the cases of blindness generally believed to be congenital.

Artificial illumination is more trying to the eyes than daylight, but, when its use is necessary, the risk of injury may be reduced to a minimum. There is little choice between oiland gas-light of a similar illuminating power. Mr. Carter remarks, "The best illumination for all purposes of close work is that of a Silber Argand burner, it matters not whether for gas or oil, placed to the left front of the worker, a little above the level of the eyes, fitted with a shade to reflect light upon the table and to intercept it above, and with the addition of an alum screen when the heat is objectionable." When several lights are used, they should be grouped together, as all cross-lights are distressing to the eye. Mr. Carter recommends that the least exacting kind of work should be done in the evening or at night; and, for literary men, reading and study by day and writing at night is the best arrangement. Reading in cars or other moving conveyances, and the close use of the eyes by dim or unsteady light, are universally condemned. Smoke is injurious to the eyes and eyelids, but, aside from its external irritating effect, Mr. Carter does not agree with some older writers in the opinion that tobaccosmoking produces any material injury to the eyes or optic nerves. According to the same authority, colored glasses should not be used except under competent surgical advice. But where protection is desired for healthy eyes from the glare of a strong light, or from reflection on snow or water, pale cobalt-blue or neutral gray is to be preferred to green or very dark glasses.

tance. No other English colony has relatively made such progress during the last ten years. The population has doubled and the production has quadrupled. According to the statements of the English colonial office, the imports, which in 1867 amounted to £20,590, had in 1878 increased to £35,040. The exports, amounting in 1867 to £15,460, had increased in 1878 to £55,470. The population in 1867 was 705, and in 1878 it had increased to 1,394. The value of the exports relatively to the number of the inhabitants is £40 to each; while in Australia it is £19 to each, and in the United States it is £4. The balance of trade in favor

of the colony is equivalent to £15 for each inhabitant.

FERTILIZERS. The system of agriculture which consists in removing crops without restoring the plant-food they take from the soil, and which Liebig aptly called Raubbau (robbery-culture), has already reduced the soil of our older States to the condition where it must be fertilized or abandoned; where not only the most careful tillage, and husbanding of the manurial resources of the farm, but also the importation of plant-food from outside, are requisite to the restoration of fertility. Guano, phosphates, potash salts, and the like, have become with us, as in Europe, indispensable to successful agriculture.

Every one of the Atlantic, and many of the Middle States, employ large quantities of commercial fertilizers. Their use is extending to the prairies of Indiana and Illinois; and even in Kansas experiments are being made with them on soil stated to be "worn out with long cropping." Single towns in Connecticut are said to expend $20,000 per annum in artificial manures, and the State of Georgia imports annually some $5,000,000 worth of plantfood, in the form of phosphates, guano, potash salts, and the like, to restore fertility to her soils. The amounts of these materials sent out from the central markets in the spring of 1881 were so great as to make, in some places, a railroad blockade. The Commissioner of Immigration of Georgia says: "It is frequently stated that the immense increase of the cotton-crop since the war over that prior to 1860 is due to emancipation only. A most important factor in bringing this about has been the very general use of commercial fertilizers." The rapid improvement of Southern agriculture has been made practicable by various material agencies, of which this is one of the chief. Not freedom alone, but freedom and superphosphates, are giving us the "New South."

How important a factor of the agricultural progress of the country commercial fertilizers have become is illustrated by the following figures, partly official and partly general estimates, but doubtless reasonably correct:

The Commissioner of Agriculture of the State of Georgia reports that the number of tons of commercial fertilizers inspected in that State in 1881 was 152,464, from which the State received $76,232 (a tax of fifty cents being levied upon each ton consumed in Georgia). Dr. Dabney, Director of the Agricultural Experiment Station of North Carolina, reports, under date of December 15, 1881, that 50,000 tons were consumed in 1878, 60,000 tons in 1879, and 80,000 tons in 1880; and that "the sales this year (1881) will slightly exceed this last amount."

It is estimated that Virginia consumes over 40,000 tons; Pennsylvania, over 50,000 tons; New Jersey, over 20,000 tons; New York, over 35,000 tons; Ohio, over 15,000 tons; New England, over 50,000 tons; and the use

of fertilizers is rapidly increasing toward the Mississippi Valley, and through Michigan, Indiana, and Kentucky. The consumption in the Atlantic and Middle States is estimated at not less than 500,000 tons, or about $20,000,000 worth. Thousands of farmers, therefore, must be using fertilizers successfully, else why this constantly increasing consumption?

The term commercial fertilizers properly applies "to those articles occurring as natural deposits, like guano and Chili saltpeter; or manipulated in some way, like dried blood and fish-scrap; or regularly manufactured, like superphosphates and potash salts, which are powerful fertilizers, are expensive in comparison with farm manure, and are regularly quoted in our market reports."

The history of the trade in commercial fertilizers dates back not more than about forty years. The value of bone, fish, and even of superphosphate of lime, however, was recognized long ago in farm practice. "The first settlers in this country learned of the aborigines on the coast that a fish, planted in each hill of maize, greatly increased the crop; bones were used as manure in England, to some extent, early in this century, and superphosphate of lime was made and applied by Sir James Murray, in England, as early as 1817."

In 1840 the first cargo of Peruvian guano was shipped to Europe. This date may be said to mark the beginning of the use of commercial fertilizers in agriculture. In the same. year appeared Liebig's "Chemistry, in its Applications to Physiology and Agriculture,' which book, with his other contributions to the subject, made the beginning of that movement which has created a science of agriculture, and has enabled the art of agriculture to meet the demands of modern life.

It is a not uninteresting coincidence that two movements of such moment for agriculture, artificial supply of plant-food to soils and the rational application of science to their culture, should have received their first great impetus at the same time. The ingredients to which the efficacy of the more common commercial fertilizers is mainly due are three-nitrogen, phosphoric acid, and potash. Among the more important sources of these materials in the American markets may be mentioned:

Nitrogen (ammonia).-The chief sources of nitrogen are: nitrate of soda and sulphate of ammonia, which supply nitrogen without phosphoric acid or potash; the various forms of slaughter-house refuse, dried blood, azotin, tankings, etc., which contain nitrogen with some phosphoric acid; and fish-scrap and Peruvian guano, which furnish both these ingredients in considerable quantities, the latter containing also some potash.

Phosphoric Acid.-The most important phosphatic materials are: bone-black, Canadian apatite, Navassa and South Carolina phosphates, and sundry "rock" or "washed " guanos, as Curaçoa and Orchilla, which supply

The present extent of this industry and the use made of fish-manures may be gathered from the fact that, in 1875, the nitrogen derived from fish-manures was equal to that contained in 30,000 tons of Peruvian guano. In 1880 there were 79 fish-factories on the Atlantic coast, employing 449 vessels and 3,200 men; 2,035,000 gallons of fish-oil were produced, and 45,000 tons of scrap. The various kinds of animal refuse, dried blood, tankings, fish-scrap, etc., are used chiefly for "ammoniating" superphosphates.

Peruvian Guano.-This wonderful material, whose use by millions of tons has done so much to restore fertility to the depleted soils of Europe and America, has been in the past the most important of the various commercial fertilizing materials. Peruvian guano, as is well known, consists mainly of the excrement of birds, which has been accumulating for centuries on the almost rainless coasts and adjacent islands of Peru and Chili. What makes the excrement of birds particularly valuable as a fertilizer is that the excretion of both kidney and intestines is mixed in the cloaca, and voided in a comparatively solid condition. What makes guano so far superior to any fresh manure of the kind is that the sole diet of these birds was fish, which are rich in phosphoric acid and nitrogen, and also that all the moisture was speedily taken out of the mass by the dry, hot winds continually passing over it. It is interesting to note that our lands are continually suffering a loss in nitrogen and other elements of plant-food which, through various channels, finds its way continually to the ocean and passes out of our reach; and that through the agency of these birds many million tons of these same elements have been recovered from the ocean, and stored up where of all places they would keep best for our use, long before we felt the loss and desired its replacement. The use of guano as a fertilizer dates back at least to the time of the Incas in the twelfth century. The old Peruvians had a proverb to this effect:

"Guano can work miracles,

Though it is not numbered with the saints." Humboldt brought samples to Europe, the analyses of which were published in 1806. A more complete investigation was made by Liebig and Wöhler in 1837. In 1840 a shipload was brought to England, and since then many million tons have been taken to Europe and to this country. Of late the supplies of Peruvian guano have been curtailed and unreliable, partly because of the exhaustion of some of the deposits, and partly because of the misgovernment and war in Peru. The future of the Peruvian guano supply it is impossible to forecast. The supply for the coming year is said to be assured, and it is the opinion of those in position to judge, that, with a stable and enlightened government, Peru may supply Europe and America with guano for years to

come.

Phosphatic Guanos and Rock Phosphates.Peruvian guano being little exposed to rain, has retained a large portion of its soluble constituents. Many of the bird deposits, however, are subject to more or less frequent rains, which either wash back into the ocean the freely soluble materials, or bring them into reaction with the coral limestone by which they are in part retained. As a rule, the nitrogen and potash are lost, while the phosphates are retained and become a valuable source of phosphoric acid, forming what are called the phosphatic guanos. In former years we received a great deal of this material from some small Pacific islands of coral formation under the name of American guano. In 1856 the United States assumed the protection of all the guano islands in the Pacific which lay within 10° of the equator north and south, and between longitude 150° and 180°. The islands chiefly worked were Baker's, Howland's, and Jarvis's. The guano was brown, pulverulent, and coarse-grained, and could be shoveled without picks. It contained from thirty to forty per cent of phosphoric acid, and by treatment with sulphuric acid made excellent superphosphates. For some time past, however, the whole product has been carried to Europe. Our main supply of this material comes now from the West Indies. Just at the mouth of the Gulf of Venezuela, in the Caribbean Sea, lie Great Curaçoa and Little Curaçoa Islands. For some years they have furnished large quantities of guano to Germany and the United States. The Little Curaçoa guano from which most of our supply comes is poorer in phosphoric acid than the other, averaging from twenty-five to twenty-eight per cent. Its mechanical condition, however, is better. Great Curaçoa guano goes largely to Germany. It is hard and rocky, but has from thirty-eight to forty-two per cent of phosphoric acid. Another phosphatic guano, which has been used to considerable extent in this country, is the Orchilla, which has a somewhat similar composition, though it is of rather inferior value and importance. Another rock phosphate from the West Indies, the Navassa, is now extensively used in this country as material for the superphosphate manufacture. The phosphatic deposits of Navassa Island were formed under water and thrown up by volcanic action. The phosphate is inferior to the phosphatic guano mentioned, especially because of a large content of iron and alumina, which causes superphosphates made from it to "revert" badly.

South Carolina Phosphates.-Dr. Jenkins, in the article already referred to, speaks of this as follows: "The South Carolina phosphate beds I believe are, and for some time will be, the chief source of raw material for our domestic superphosphate manufacture.

"For most of the facts given in this connection I am indebted to an interesting printed report by Professor C. U. Shepard, Jr., of

Charleston, who has had a more extensive experience in the matter than any one else, and to verbal information received from him. As to the real extent of the deposits which can be worked to advantage, we at present are not fully informed, for the industry is still in its infancy. The existence of vast beds of phosphorite was known before the war, but they were not worked till after its close. This material is found in many places on and near the sea-coast, but the larger part hitherto marketed has come from the region lying to the north and northwest of Charleston between the Cooper and Stono Rivers, and from the region at the head of St. Helena Sound on the Bull and Coosaw Rivers northeast of Beaufort. "It is essentially a phosphate of lime soft enough to be got out with shovel and pick. The land deposits occur in a stratum from six to fifteen inches thick, though averaging not more than eight inches, and where worked do not lie more than six feet below the surface.

"There are also submarine deposits consisting both of loose material brought down by the current, and of fine regular strata. This is known in the market as river rock.'

"The rock is always washed, drained, and dried somewhat before shipment, and some firms dry their material thoroughly by piling it up under cover around tubes which are supplied with hot air. Hot-air dried cargoes at present make up more than half the total amount shipped.

"The extent of the industry is indicated by the following figures:

"There were shipped from Beaufort and Charleston the following amounts of crude phosphate: In 1875, 122,790 pounds; 1876, 132,626; 1877, 163,220; 1878, 210,323; 1879, 199,365; 1880, 190,763; 1881, 266,734."

Apatite. Very large deposits of the mineral apatite have been opened in Canada, and are being utilized for the manufacture of superphosphate. It is said, however, that the bulk goes to England, the market rates being at present such as to make other materials, as South Carolina phosphates, cheaper for our home use. The apatite, however, makes an excellent fertilizer, and the supplies are, fortunately, very extensive.

Bone-Manures. Of these, the most important are bone, raw, boiled, and steamed, boneblack, and bone-ash. Bone is offered to the farmer almost everywhere and in a great variety of forins, and is, perhaps, more widely used than any other concentrated manure. Raw bones contain from 3 to 4 per cent of nitrogen, and from 20 to 25 per cent of phosphoric acid. Steamed bone is generally a little poorer in nitrogen and richer in phosphoric acid, while bone which has passed through the glue-factories contains often but a small fraction of one per cent of nitrogen, and may run as high as 30 per cent of phosphoric acid. Bonemanures vary in mechanical condition as well as in composition. Very fine-ground bone

acts quickly, but coarsely ground bone, especially if greasy, is one of the slowest of fertilizers to decompose in the soil and furnish its material to the plant. Adulterations of bone with intent to defraud are not frequent. A great quantity of very coarse bone is used, but boiling and steaming, which remove the fat and make the bone friable and easily ground, is becoming very general, and the result is a great improvement in the quality of bone-manures. The spent bone-black from sugar-refineries furnishes a small but constant supply of material, not suited for direct application to land, but much prized as a basis for superphosphate because of its fineness and convenience for treatment with sulphuric acid. Even when genuine bone-black is out of the market, manufacturers bent on satisfying their customers continue to turn out this popular superphosphate by a judicious mixing of mineral superphosphates and lamp-black. Bone-ash froin South America is occasionally found in the markets.

Potash and the German Potash Salts.— The question whence the potash for the depleted soils of the world was to come, was for years a serious one with chemists and agriculturists. Wood-ashes were a very limited and withal costly source, and did not supply enough for use in manufactures and other than agricultural arts. The extraction of potash from orthoclase feldspar and from sea-water, though feasible, was too costly. The solution of the difficulty was found a few years ago in the discovery of the potash deposits in the region of Stassfurt, in Germany. This accumulation of salts has come from the evaporation of sea-water in past geologic time. The process of evaporation, whose cost, when carried on by artificial means, would be so great, has been provided for by nature on an enormous scale, and we have the products in the deposits referred to. Commencing near there but a few years ago, the use of potash salts as fertilizers has already become almost universal in Germany, has extended largely into other parts of Europe, has reached to the impoverished fields of our own country, and even to the coffee-plantations of Brazil and Ceylon. amount used has increased from a few hundred to many thousand tons per year. The Stassfurt fertilizers have excited an interest and reached an importance comparable with that to which Peruvian guano attained years ago. The results of a great deal of experimenting and experience indicate that the usefulness of these salts as fertilizers depends not only upon the character of the salts themselves, of which there are various grades, but also on the kind of soil, the mode of application, and the kind of crop. Properly used on soils deficient in potash, they are extremely beneficial and profitable. A singular fact in connection with the Stassfurt mines is that the potash compounds were at first thrown away. The mines had been opened for the sake of the salt, of which they supply immense quantities. On the layer

The