As scarcely any oysters were shipped farther inland, it was necessary that the price should fall rapidly if the oysters were not to spoil. And this rapid fall in the price of oysters preserved the beds from being exhausted. But as soon as the railroads brought fresh oysters to the inland cities the number of oyster-eaters increased, and thus the demand for oysters likewise increased from year to year in spite of the rapid rise in the price. I think that this has caused a more reckless fishing of oysters since 1852; and this conviction is strengthened by the fact that at the inspection of 1869 there were only 282 half-grown oysters to 1,000 fullgrown ones, instead of 421, as in former years, and during the five inspections held, 1872 to 1876, this number had decreased to an average of 107. Many Englishmen who are theoretically and practically well versed in everything which concerns the oyster think that the rapid decrease of the number of oysters is not caused by too reckless fishing, but try to explain the fact by a series of years unfavorable to the breeding of the oyster. According to their statements no considerable number of oysters has been bred since 1857-59. This may be true with regard to some oyster-beds, but it has no influence on the general oyster-trade on the western coasts of Europe, as this is not dependent on particularly favorable summers, but on the average climate. And, according to observations made by the Paris Observatory, since 1806 this average climate has remained the same during this century, which has witnessed the total depletion of some West European oyster-beds. If the average profit from a bed of oysters is to remain permanently the same, a sufficient number of mother-oysters must be left on it, so as not to diminish the capacity of maturing. For if all the destructive causes continue in the same degree, the capacity of maturing must decrease in the same proportion as the number of oysters capable of propagating is diminished. If an oyster-bed is to retain its usual capacity of maturing, even when its productiveness is diminished, the causes which destroy young oysters must be diminished. This can be done : 1. By increasing the number of places to which young oysters can cling. 2. By diminishing the number of enemies of the oyster. This can only be done under such favorable natural conditions as in Arcachon and some other places on the French coast, at least on such a scale as to make the profitable cultivation of the oyster possible. As we cannot cultivate it on our coasts, it is our duty to regulate the fish. ing in our natural oyster-beds in such a manner as to make them produce permanently the highest possible average quantity of oysters. As the annual increase of half-grown oysters is 421 to every 1,000 full-grown oysters, not more than 42 per cent. of these latter ought to be taken from a bed during a year. It is best only to take the older of the full-grown oysters, in order that the fully matured ones may get as large and as fat as possible, and produce the greatest possible number of young ones before they are brought into the market. Every oyster-bed where fishing is going on ought to be examined at least every two to three years to ascertain the following points: 1, the numerical proportion between full-grown and half-grown oysters; 2, the density of the oysters; 3, the nature of the bottom, the fauna and flora of the bed; 4, whether the area covered by oysters has been diminished or enlarged, or remained the same. If movable bottom in the neighborhood of a bed becomes firm, it should be covered with oyster-shells or other objects to which the young oysters may cling. If a bed has become filled with sand or clayey mud, it ought to be cleaned with oyster-nets or harrows. Wherever circumstances permit, the enemies of the oyster ought to be kept away from the beds as much as possible. As not all beds produce oysters of the same fine quality, experiments ought to be made to show whether young, half-grown oysters of an inferior quality will improve in flavor if transplanted to other beds having better oysters. This ought, however, not to be done systematically if the productiveness of the beds seems to suffer by it. The sea-water which daily flows over the bed contains only a certain limited amount of nutritious matter, and there is a possibility of this being exhausted. If the number of oysters produced by a bed is doubled by introducing oysters from other beds, only half the quantity of food comes to each oyster, and its growth is retarded. It is fortunate that the Schleswig-Holstein oyster-beds are the prop. erty of the state. If everybody could fish there, they would soon be exhausted. If they are to remain a permanent source of profit to the whole population of the state and of special profit to the inhabitants of the coast, the quantity of oysters to be taken annually ought not to be determined by the price of the oysters, but solely by the annual increase. Oyster-beds ought to be worked on exactly the same principles as the state forests, with a view to the welfare of the present and future population of the whole state. XIX.-EXPERIMENTS UPON THE TIME OF EXPOSURE REQUIRED FOR ACCURATE OBSERVATIONS WITH THE CASELLA-MILLER DEEP-SEA THERMOMETER. BY COMMANDER L. A. BEARDSLEE, U. S. N. UNITED STATES STEAMER BLUE-LIGHT, SIR: In compliance with your request that I should examine and compare the thermometers, standards and others, belonging to the United States Fish Commission, I have carried on a series of experiments with them, the results of which I herewith submit to you as one of the results of the summer's work of the Commission. The instruments delivered by you to me to examine were the following, arranged and numbered according to their sensitiveness as developed during experiments: No. 1. A mercurial standard, made by L. Casella, of London, No. 7,432, reading from zero up to 1200, on a scale marked on the glass, and twelve inches long, giving ten degrees to the inch'; bulb cylindrical, .75 of an inch in length. No mounting; sensitive to the slightest change, and rapid in action. No. 2. A mercurial standard, No. 16,578, made by James Greene, New York, reading from zero up to 120°, on a scale marked on the glass, and four and four-tenths inches long, giving twenty-seven and two-tenths degrees to an inch; bulb cylindrical, seven-tenths of an inch in length. No mounting; as sensitive as No. 1, and agreeing closely with it. No. 3. A mercurial standard, no number, made by James Greene, New York, reading from 500 up to 105°, on a scale of six inches, marked upon a metal-back mounting. Very sensitive, but not convenient, on account of limited range. No. 4. A mercurial standard, no number, made by Tagliabue, of New York, reading from 50 below zero up to 125°, on a scale 7.8 inches long, equal to nearly 16° to an inch; scale marked on a metal-back mounting; bulb spherical, with a brass guard. Moderately sensitive, but slow in action. No. 5. A United States Navy mercurial thermometer, mounted with metal back and cup guard; spherical bulb; scale marked on back. Moderately sensitive, and fair in action. No. 6. A Casella-Miller self-registering deep-sea thermometer, No. 15,720. No. 7. The same, No. 17,017. |