An official notice from the Post-office states, that from the first of the present month London is to be placed on the same footing, with respect to letters, as the rest of the country--that is, they must either be stamped before being posted, or sent unpaid. This is a measure which will materially diminish the labour of keeping accounts at the central office; and the more that labour is saved, the more will there be left to facilitate postal communication. Books and periodicals can now be sent to most of our colonies at the rate of a shilling a pound--a fact which those who have hitherto sent their parcels at any one's trouble and expense but their own, will do well to bear in mind. Ocean Penny Postage is growing into favour, and is talked about in such a way as to shew that the project will not be left to take care of itself.
The French are going to send a new Scientific Exploring Expedition to South America, chiefly for researches in Brazil and Paraguay. Perhaps the veteran Bonpland, who was so long detained by the dictator Francia, may be induced to come home in it, as he has written to express his desire of returning to France. And something has been said at Washington, about sending a couple of frigates to survey the great river Amazon, in which, as the official document states, there is a sufficient depth of water to float a large ship at the foot of the Andes, 1500 miles from the sea. America will surely be well known some day. Meanwhile, we are extending our knowledge of Africa; a map of that country is about to be published, comprising the whole region from the equator to 19 degrees of south latitude. In this the recent discoveries will be laid down, and we shall see Mr Galton's route of 1600 miles from Walfish Bay to Odonga, near a large river named the Nourse, and to the country of the Ovampo, described as an intelligent tribe of natives. We shall find also, that the snow-peaked mountains seen by the German missionaries, and considered to be the source of the White Nile, are not more than about 300 miles distant from the eastern coast; and it is said that no more promising enterprise could be undertaken, than an attempt to ascend and explore them, starting from Mombas. Barth and Overweg were at the eastern end of Lake Tchad when last heard from; and we are told that the slave-traders, finding their occupation decreasing on the western coast, have lately, for the first time, penetrated to the interior, and tempted many of the natives to sell their children for showy European goods. Lieutenant Macleod, of the Royal Navy, proposes to ascend the Niger in a steam-launch, and when up the country, to cross over to, and descend the Gambia, with a view to discover new sources of trade; and Mr Macgregor Laird is still ready to carry a vessel up any river of the western coast to which government may please to send him. Besides the travellers mentioned, there are others pushing their way in different parts of the south; and the French are not idle in the north--they have added to our information concerning Abyssinia, and the countries bordering on the Great Desert. But in addition to African geography, all these explorations have added to our knowledge of African geology. A vast portion of the interior is supposed to have been an inland sea, of which Ngami and other lakes are the remains; fossil bones of most peculiar character have been found, but only of terrestrial and fresh-water animals. A name is already given to a creature of a remote secondary period; Professor Owen, from the examination of a few relics, pronounces it to be a _Dicynodon_. According to Sir B. Murchison, such have been the main features of Africa during countless ages; 'for the old rocks which form her outer fringe, unquestionably circled round an interior marshy or lacustrine country, in which the dicynodon flourished at a time when not a single animal was similar to any living thing which now inhabits the surface of our globe. The present central and meridian zone of waters, whether lakes, rivers, or marshes, extending from Lake Tchad to Lake Ngami, with hippopotami on their banks, are, therefore, but the great modern, residual, geographical phenomena of those of a mesozoic age.'
The publication of special scientific works is going on under the auspices of different European governments. The Batavian Society of Rotterdam have just issued an elaborate illustrated Report on the best method of improving permanently the estuary of Goedereede--a question of considerable moment to the merchants of Rotterdam. The French government have had a new fount of Ethiopic types cast, to enable M. d'Abbadie to prepare a catalogue of African manuscripts. And our Secretary of State for the Home Department has presented various libraries and public institutions with two portly folios, entitled _Liber Munerum Publicorum Hiberniæ, or the Establishments of Ireland, from the Nineteenth of King Stephen to the Seventh of George IV._, which we may accept as an addition to the _Memorials of History_, commenced two or three years since. Then, as a private enterprise, we have a scheme for a new edition of Shakspeare, in twenty volumes folio, which is to be completed in six years, with all that can be required in the way of illustration, be it archæological, philological, historical, or exegetical. Mr Halliwell is to be the editor; and it is said that not more than 150 copies will be printed. Another birth for the spirit of the dust that lies in the tomb at Stratford.
Research is as active as ever in France. M. Bernard, who is well known as a physiologist and anatomist, after a careful study of the salivary glands, finds that each of the three, common to nearly all animals, furnishes a different secretion. The saliva from the sublingual gland is viscous and sticky, fit to moisten the surface of substances, but not to penetrate them, giving them a coat which facilitates their being swallowed. That from the parotid gland, on the contrary, is thin and watery, easily penetrates substances taken into the mouth, and thereby favours their assimilation; while the saliva from the submaxillary gland is of a nature between these two. These facts were verified by soaking portions of the membrane in water, as well as by experiments on the living subject; the liquid in which they were soaked presented the same character as that of the secretions.
The varying of the parotid secretion with the nature of the food taken, is considered by M. Bernard to be a proof that this secretion is especially intended to favour mastication. A horse kept on perfectly dry food gives out a far greater quantity than when the food is moistened. Experiments on the dog and rabbit supplied similar results; and, extraordinary as it may appear, the gland will secrete saliva in the course of an hour weighing eight or ten times as much as its own tissue. A striking example this of the rapidity with which saliva can be separated from the blood under certain circumstances, and of the fallacy of founding conclusions on the quantity secreted within the twenty-four hours.
The sublingual gland is inert during mastication, and only begins to act as swallowing commences, when it envelops or lubricates the chewed substance with a fluid that assists its passage to the stomach. The function of the submaxillary has much to do with taste; the fluid which it pours out dilutes and diminishes the pungent flavour of sapid substances, and at the same time weakens the energy of their contact. The three organs are identical in texture, though so different in their secretions; 'each gland,' as M. Bernard says, 'having a special act, its function is exercised under separate and independent influences. Notwithstanding their discharging into and mixing in the mouth, their use remains distinct,' as above stated. To complete this brief summary of an interesting subject, it may be added, that birds and reptiles have but one kind of saliva, answering to the viscous in mammalia.
M. Vogt, in a communication to the Académie, adds to the proofs that what is called the spontaneous generation of certain worms, is due to natural causes. For instance, a worm, which has no reproductive organs, is often found in the body of the stickle-back; this worm, however, is known to breed, but it does so only when the stickle-back happens to be eaten by a bird; the worm is then placed in the proper condition for development, 'for it is then only that its segments become filled with eggs, which, egested by the bird, pass into the bodies of other fishes;' in a way more in accordance with natural operations than spontaneous generation.
Again, of two kinds of worms which infest human beings, the _Bothriocephalus_ is found among the Poles, Swiss, and Dutch, while the _Tenia_, or tape-worm, is common among the French and Germans. If, however, the latter reside in Switzerland, they also become infested with the first-named worm, the reason given being, that in Switzerland liquid _excretæ_ from cesspools are largely used for manuring vegetables, and that, in the eating of these vegetables, the eggs of the worms are taken into the body, and become hatched by means of the intestinal warmth. These investigations, which are to be continued, are important, seeing that they have a bearing on the phenomena of health and disease.