the shell altogether, entangled amongst the strands of the byssus. When the pearl banks are under constant supervision, the causes leading to the formation of pearls, as yet imperfectly understood, will, doubtless, receive close attention.

It now only remains to describe the plan by which it is hoped that, in future, the Tinnevelly pearl banks will be kept supplied with a sufficient number of well-grown shells to supply a remunerative annual fishery. The idea was suggested by the method adopted with regard to edible oysters on the English and French coasts. The chief external difference between the pearl and edible oyster is, that the former secures itself to rocks and stones by means of a byssus, while the latter merely lies flat on the ground on its convex side; but there is no reason why the pearl oyster should not thrive on artificial banks as well as the edible oyster.

In the Colne oyster fishery, the brood (oysters two years old) are dredged up out at sea, and placed on "layings" within the river Colne. These "layings" are about 100 or 150 yards by 80, according to the breadth of the channel, most of them dry at low water, and they are paved with stones, old shells, and any other hard substances, to a depth of a few inches, so as to form a bed for the oysters, which would be choked in soft mud. This material is called culch. In France, M. Coste has adopted a system of placing fascines on the layings, instead of culch, as resting places for the oysters; but the natural advantages of the ground render any artificial method of this kind unnecessary in the Colne. It is very important that the culch should be kept perfectly clean and clear of mud, and, above all, that every mussel-shell should be weeded out. The mussels have a remarkable tendency to collect mud round them in heaps, probably owing to their elongated shape, and if they are allowed to remain on the layings, there is danger of the oysters being choked with mud. The oysters remain on the layings for two years, when they are fit for eating, and during this time there are constant examinations, in order that all dead fish may be removed, and the culch kept clear of mud. In places where the layings are never laid bare by the tide, this is done by means of a dredge, all live fish and culch being carefully thrown back, while dead fish, soft mud, and mussels are removed.

There can be little doubt that some such system might be adopted in rearing pearl oysters, and Dr. Kelaart says that "he sees no reason why pearl oysters should not live and breed in artificial beds, like the edible oysters, and yield a large revenue.' He has ascertained, by his experiments in Ceylon, that the pearl oysters are more tenacious of life than any other bivalve with which he is acquainted, and that they can live in brackish

water, and in places so shallow that they must be exposed for two or three hours daily to the sun and other atmospheric influences. Captain Phipps, the superintendent of the Tinnevelly pearl banks, has come to the same conclusions; and, convinced that artificial nurseries for the young oysters are the only means by which remunerative fisheries can be ensured, he has proposed the following plan, which has been adopted :-

The harbour of Tuticorin is formed by two long islands, and between them and the mainland there is a bank about three miles long by a quarter of a mile broad, with a depth of from three to seven feet, entirely free both from surf, currents, and influxes of fresh water. Captain Phipps proposes that this bank should be walled round with loose coral until it is formed into a basin, the edges rising three feet above high water mark. Over the bed of the shallow basin thus enclosed, live coral will be regularly spread, so as in a few years to form a solid mass, serving the purpose of culch, and the basin will be divided into three parts, one for the old oysters, and the other two for the young ones that may be in process of rearing. After the division of the basin set apart for breeding has been stocked, it will be carefully watched, and when the spawning has taken place and the young oysters are well formed, they will be removed from the old oysters and rocks to which they are attached, and placed in one of the separate parts of the basin, and the same plan will be followed each succeeding year. On reaching a sufficient age, they will again be removed to one of the pearl banks in the open sea. The last operation is necessary, because it would be impossible to enclose an artificial space which would hold as many grown oysters as are required for a remunerative fishery, and because it is believed that the quality of the pearl depends on the depth and clearness of the sea in which it has been formed.

A single oyster, five or six years old, often contains no less than 12,000,000 eggs, and in the fishery of 1861 the total number taken only amounted to 15,874,500, so that the number of young ones annually obtained from the nursery will be abundantly sufficient to stock banks for each year's fishery. Care will of course be taken that only such banks are selected for stocking as have the rocks which compose them raised well clear of the surrounding sand.

By this system, adapted as it is from those of the English and French edible oyster fisheries, several advantages will be secured, and all the dangers to which the pearl oysters are now exposed will be avoided. The young growing molluscs, safe on their carefully watched laying at Tuticorin, will be secured from the choking sands of their natural banks, as well as from their alleged enemy, the soorum, the effects of which

are probably the same as those caused by the mussels on the edible oyster layings in the Colne. It is during the period of their growth that the pearl oysters are so exposed to these dangers, and very frequently banks have been found well stocked with young oysters, and giving promise of a lucrative fishery, at a preliminary examination, which, when the time for the fishery arrives, are bare, all their inhabitants having died and been washed away. But if preserved during the period of growth in the artificial nursery, and only placed out when they have reached maturity, the oysters can then form their pearls in security until the season for the fishery arrives, and well stocked pearl banks may be reckoned upon for each year.

Thus it is hoped that, by adopting these carefully considered plans, and improving upon them as experience and watchful investigation dictate from year to year, a regular and unfailing source of revenue will be secured to the State, and the Tinnevelly pearl banks will, after laying dormant for thirty years, regain the immemorial renown which was conceded to them, alike in the days of Ptolemy, of Marco Polo, and of Hamilton. They form the most ancient fishery in the world, and, now that science and careful supervision have been supplied, they will no longer be the least remunerative.

MICROSCOPE TEACHINGS.*

Ir is very easy to write a popular twaddle about science, but rare is the talent by which science is really popularized. For the first and useless performance, very slender knowledge is required, but the last requires both accuracy and depth. It also demands the enviable faculty of reducing a subject to its simplest elements, and presenting them in a pictorial and suggestive form. It is not enough to narrate facts, for unless they are judiciously expounded they remain in the mind as so many dead seeds destitute of germinating power. We often see this in pupils who have been well crammed by Mr. Feeder, B.A., or by his feminine counterpart, who is stuffed with Magnall's questions, impregnated with latitudes, carries dates on her fingers' ends, and diffuses an odour of the rule of three. The more people are taught after this fashion, the greater nuisance

* Microscope Teachings: Description of various Objects of especial Interest and Beauty adapted for Microscopic Investigation, illustrated by the author's original Drawings, with Directions for the Management of a Microscope, and the Collection and Mounting of Objects. By the Hon. Mrs. Ward, author of Telescope Teachings. London: Groombridge and Sons.

they are to their neighbours, and the less serviceable their minds become to themselves. They do not, properly speaking, know anything, because reflection has never been cultivated, and their imaginations have grown dull under a cumbrous load of ill-assorted materials. Widely different is the result of real teaching, whether its lessons are communicated orally, or reach the student through the medium of books. This is always conducive to mental growth and health, whatever form it takes, but perhaps never more so than when it charms the eye and the fancy with scenes of beauty from the world of nature, and extracts its lessons of wisdom from objects that gleam upon us from the heavens, or surround us on the earth. The advanced students of nature, if fitted for their work, are in the position depicted by Wordsworth in his Prelude. Without wrongful egotism they may exclaim,

and it is indeed a noble task to be the pioneers and guides into regions of truth and loveliness, infinite in their variety, perennial in their charm.

To the Hon. Mrs. Ward must be assigned an excellent place among these pioneers and guides. In her Telescope Teachings she has provided an admirable beginning for astronomical study, and her work on the microscope is by far the best that has been produced for the particular object its author had in view. It is, as befits an introduction to a delightful branch of practical science, an elegant book, enjoying all the advantages of excellent paper, large type, beautiful coloured plates, and handsome binding. The moment it makes its appearance in a civilized family there will be a rush towards it, and it will seldom fail to convert its readers into microscopists if they can obtain an instrument to work with as it directs.

Microscope Teachings is divided into twelve chapters, the two first giving very clear and useful information on microscopes, and the various processes and precautions necessary for their use. This will prove valuable to many purchasers of instruments, who often experience bitter disappointment after the optician has sent their instrument home, because no one is at hand to explain the details of manipulation, without which nothing but failure can arise. With Mrs. Ward's book they would make no mistakes, and her advice would guide them wisely in the selection of an instrument according to the expenditure they wished to make. Beginners should not be caught by the glittering appearance of a new microscope, and the number of articles supplied for a given sum. What they want is "that the microscope shows objects clearly, and is perfectly

achromatic, that is, without those fringes of rainbow colours always seen surrounding objects in inferior microscopes. It should also be constructed to lean backward, as being far less fatiguing to the observer than the upright position. It should have at least two different degrees of magnifying, and one of them should be of low power, with large field of view, for the purpose of showing as much as possible of an object at once. These, with the condensing lens, and mirror to throw light on or through objects, are things indispensable." A reference to our advertising pages will show how cheaply these necessaries can be obtained, and although those who have money to spare will be sure to want a superior instrument if they continue the pursuit, a comparatively simple one, judiciously selected, will serve all ordinary purposes of investigation or display. After giving information and advice, which every beginner will be glad of in learning to use a microscope, Mrs. Ward describes the methods of collecting and mounting objects, and then, in the fourth chapter, begins her list of objects with the structure of insects' wings. This chapter is illustrated by many, exquisitelydrawn, and coloured, figures from her own pencil, and is appropriately followed by another chapter on "the scales of insects and fish," which likewise supply beautiful plates. The objects described in these and other chapters are for the most part casily obtainable, and this is important, because, although it is both useful and pleasant to have a collection of slides prepared by professional mounters, the most substantial knowledge will be gained by collecting and mounting for ourselves. Every one ought to do this to a certain extent with reference to every class of object, even if the cost of prepared slides is of no importance; and those which are bought or given will be much better understood if the student has prepared something of the same kind for himself.

As a specimen of Mrs. Ward's directions we will cite her account of how to obtain the scales of the eel-a beautiful structure, which few who are in the habit of cating the creature take the trouble to behold. Our author says, "When I first began to prepare objects for the microscope, I read in some old book that these were worth looking at, so I procured a dry piece of eel skin, but it was long before I could find what I was in search of. I scraped and scraped with a knife, and examined the scrapings with a microscope, magnifying them twenty times-forty times-perhaps 100; but no scales appeared. I forget how I contrived to make them out at last; but, if I take a little piece of eel skin, and view it as a transparent object, magnified rather more than four diameters, the first thing I see is that the skin is covered with star-like spots, and next I observe the scales lying close together. And this is the way to