may be more than its cohesion can overcome: it will therefore break. Consequently, if we pull at this twisted skein, we shall not separate it by drawing one parcel out from among the rest, but the whole fibres will break; and if the distribution of the fibres has been very equable, the skein will be nearly of the same strength in every part. If there is any part where many ends of fibres meet, the skein will break in that part. which the rope will carry. Thus, if the rope has six inches circumference, six times six is thirty-six, the fifth of which is seven tuns and one fifth. It is usual in the manufacture of large ropes, especially in those for nautical purposes, to saturate them with tar. This is often done in the state of twine or yarn, as being the bes mode by which the hemp can be uniformly penetrated. The yarn is made to wind off from one reel, and, having passed through a vessel of liquid hot tar, is wound on another reel; the superfluous tar is taken off by passing through a hole surrounded with oakum or it is sometimes tarred in skeins, which are drawn by a capstan through a tar-kettle, and a hole formed by two plates of metal held together by a lever loaded with a weight. There is this peculiarity to be noticed-tarred cordage is weaker when new than white, and the difference increases by the keeping. From some very accurate experiments, made more than half a century ago, it was found that on newlymade cordage the white was one eighth stronger than that which was tarred; that, at the expiration of three months, the difference in favour of the new was almost one fourth; and, in about three years and a half, the difference was as twenty-nine to eighteen. From these, and other experiments, it From this view of the matter may be deduced a was ascertained-1. That white cordage in continfundamental principle in rope-making, that all twist-ual service is one third more durable than that which ing, beyond what is necessary for preventing the fibres from being drawn out without breaking, diminishes the strength of the cordage, and should be avoided when in our power. It is of importance to keep this in mind. We know very well that we can twist a skein of fibres so very hard that it will break with any attempt to twist it harder. In this state all the fibres are already strained to the utmost of their strength. Such a skein of fibres can have no strength. What we have said of this extreme case is true in a certain extent of every degree of twist that we give the fibres. Whatever force is actually exerted by a twisted fibre, in order that it may sufficiently compress the rest to hinder them from being drawn out, must be considered as a weight hanging on that fibre, and must be deduced from its absolute strength of cohesion, before we can estimate the strength of the skein. The strength of the skein is the remainder of the absolute strength of the fibres, after we have deducted the force employed in twisting them together. is subjected to the operation of tarring. 2. That it retains its strength much longer while kept in warehouse. 3. That it resists the ordinary injuries of the weather one fourth longer. It may then be asked, "Why is tar ever used by the rope-maker?" Because white cordage when exposed to be alternately very wet and dry is weaker than that which is tarred, and to this cables and ground-tackie are continually subjected. It has also been pretty well ascertained that cordage which is only superficially tarred is constantly stronger than that which is tarred throughout. It is necessary then to twist the fibres of hemp together, in order to make a rope; but we should make a very bad rope if we contented ourselves with twisting together a bunch of hemp sufficiently large to withstand the strains to which the rope is to be exposed. As soon as we let it go out of our hands, it would untwist itself, and be again a loose bundle of hemp. It is necessary therefore to contrive the Mr. Hancock has discovered a process for covertwist in such a manner that the tendency to untwisting ropes with elastick gum (caoutchouck) in a liin one part may act against the same tendency in quid state, for the purpose of protecting the vegetaanother and balance it. ble materials that compose them from the destructive effects of damp, by which they are so rapidly brought into a state of decay. The hempen materials are to be soaked in a solution of caoutchouck procured from a tree common to South America and some parts of the East Indies, and is the same with Indian-rubber. As it flows from the tree it is about the consistence and much the appearance of cream. It is to be used exactly in the same way as tar is commonly used, except that it is not to be heated. Without going deeply into a process which would excite but little interest in the general reader, it may be enough to state that fibres of hemp are twisted into yarns, that they may make a line of any length, and adhere among each other with a force equal to their own cohesion. The yarns are made into cords of permanent twist by laying them; and, that we may have a rope of any degree of strength, many yarns are united in one strand, for the same reason that many fibres were united in one yarn; and in the course of this process it is in our power to give the Several coats of this body may be laid over the rope a solidity and hardness which would make it external surface of the cords, one succeeding the less penetrable by water, which would speedily other, before the preceding coat has become perfectdestroy it. Some of these purposes are inconsistently dry. After this the ropes are to be placed in a with others and the skill of a rope-maker lies in making the best compensation, so that the rope may, on the whole, be the best in point of strength, pliancy, and duration, that the quantity of hemp in it can produce. The following rule for judging of the weight such a rope will bear is not far from the truth. It supposes them rather too strong; but it is so easily remembered that it may be of use. Multiply the circumference in inches by itself, and take the fifth part of the product; it will express the tuns drying-room, moderately heated, until the gummy material on the outside of the ropes has become perfectly free from stickiness. The patentee states that ropes for ships' cables to tackling when thus prepared are equally pliable to those coated with tar: and as the material cannot crack by drying, so as to expose the internal fibres to the action of the air or damp, ropes so prepared will last much longer than by the ordinary treatment, being less liable either to external or internal injury. In China they twist together long filaments of bamboo; and this material for ropes is preferred to hemp. The above engraving is designed to represent the Chinese manner of making ropes. It bears considerable resemblance to our own method. Their cables and other large ropes, however, the Chinese spin vertically. The workmen are mounted on a high scaffold, and the rope descends, as fast as it is made, and is immersed in a liquor which renders it more strong and elastick. CONCHOLOGY. UNDER this title, or that of TESTACEOLOGY, naturalists have hitherto comprehended a systematick arrangement of shells, whether marine, fluviatile, or terrestrial it is the science by means of which that branch of natural history is distributed into genera and species. The title conchology has, however, been somewhat misapplied, having been used in a less extended sense than its etymological meaning implies; since conchylion does not express a sh II only, but the molluscous animals, whose body is altogether protracted-merely partially covered with a shell, or possessing portions of shelly matter, concealed under its skin, or in its folds, to defend certain organs most liable to external injury from their exposed situation. Such of our earlier naturalists as merely studied an arrangement of shells, detached from their parent architect, (as was, in fact, the case with nearly all of them,) have in many cases, and should in every one, have designated their systems by the term Testaceology, which is more appropriate, as not admitting any perversion of the meaning they attached to it, and clearly expressing its derivation and object-Testa, the Latin word for a shell; and Logos, a Greek word, meaning a discourse or treatise on the subject to which that word is added when descriptive of a science. The Greek writers on natural history also used the term Ostracology, which has the same meaning, and is considered by " many authors far preferable, not being a compound of two languages, a fault but too frequently observable in the terminology of all works on natural his tory. Until within about the last half century, nearly every author on this branch of nature has written exclusively on the arrangement of shells, detached from the animals inhabiting and constructing them; this, with very little exception, continued down to the period when the immortal Linnæus, who may be styled the father of systems, among others, formed one of Conchology, but, like his predecessors, it was based entirely on the form of the shell, and his genera composed from the characters it presented. This was done with considerable judgment, and many of his descriptions are extremely accurate, so far as regards external configuration, but in theory, this system is wholly artificial, and consequently bad. It is true he seems to have felt it so to a certain extent, since he has made some reference to the analogous animal which he imagined to have belonged to the shell; these he placed among his Zoophytes, but he still took no other guide than the form of the shell, and made but few inquiries with respect to the supposed inhabitant The impulse given throughout Europe by his system, and that of several other eminent naturalists, led to an extended view of the subject; their attention became drawn to the anatomical investigation of the animals themselves; and the subject presented an interest never before experienced; accounts were published of the result of these inquiries, gradually producing a different method of viewing the classification of molluscous animals; and Pallas may be considered the head of this new school, as, in fact, it was from his Miscellanea Zoologica that the first germe of improvement was derived in the arrangement of shells, since grown into its present form, though as yet, in many respects, only in its infancy. To persons who are collecting shells and forming cabinets of them only as beautiful objects of creation, the system of Linnæus may answer as well as any other, since they feel no interest in the scientifick arrangement of the species, or those won neous conclusions entertained by book-naturalists | tries where vegetation is too luxuriant to be trained and book-makers, among which are some (and those, by art to the use of mankind, covering immense too, professing to instruct the rising generation) who tracts of land with impenetrable gloom, not only have recently published a poetical description of snails, but other species of terrestrial molluscs, certain shells sailing together in little fleets-one achatina, bulinas, &c., are found, some of a very valve expanded to catch the passing breeze that large size, proportioned to the magnitude of the wafts them o'er the unruffled bosom of the vasty duties they have to perform, and in these situations deep-of others that may be supposed to pass their their voracity is said to be most extraordinaryleisure moments in playing at leap-frog with each stripping the loftiest trees of their verdure in an inother. But these, like all other tales conjured up credibly short space of time. Shall we then grudge by the magick wand of fancy, are more entertaining it a slender portion of our superfluous luxury, withthan true, and must be condemned in works whose object should be to clothe facts in the simplest garb, divesting them of the tinselled ornaments of fiction, which, though they may dazzle for a time, shortly sink before the light of truth, and are rejected as worthless. Another serious evil arises from these pretty nursery tales, that of casting a doubt upon every other assertion, however well founded in truth. out ascertaining, by actual examination and rational reflection, that this little creature was not merely ordained to devour our choicest fruit, but that it has also a duty to perform by consuming, in a far greater proportion, other things in the vegetable world that would, without them, prevent the full completion of the very object for which we ignorantly destroy a principal agent. The well-established fact, that the eggs of these animals have been absolutely baked, during six months, under the scorching rays of a tropical sun, without destroying the germ of life, proves, could no other facts be adduced, that nature has vested in these creatures certain important uses and powers far beyond our short-sighted views; and it must lead a philosophical mind to conclude, that in this instance, as well as in many others equally remarkable, we stubbornly close our eyes to the good that is forced upon us. We think we hear it said, that in advocating the cause of snails, we have never had the mortification of seeing our ripe and delicately painted peaches disfigured by their hungry propensities. Be that as it may, we have also observed, that they, like ourselves, when no such treat presented itself, were content with humbler fare, and as industriously as voraciously consumed other objects, to us useless, or noxious as food, never desert ing the purpose of their existence, though that end is not yet fully revealed to us. As an article of food, they are entitled to our consideration; for, though they form no part of our gastronomick delicacies, they nevertheless were considered such by the Roman gourmand; and even down to the present day, snails form an important article of nourish. ment and commerce in Germany, France, Spain, Italy, Turkey, and the Levant. This digression leads to a conclusion, constantly to be drawn by every reflective mind, that from the colossus of bivalves (the Tridacna gigantea) whose inhabitant would satiate the "sharp-set appetites of a hundred men," down to the shell less than a grain of sand, each is endowed with similar mechanical powers and bodily faculties, adapted to its sphere of action in the place it is destined to occupy, the one and the other playing an equally important part in this crumbling theatre of mortality, and forming so many connecting links of the chain that binds together the invisible operations of nature under the directing wisdom of omnipotence. An instance may here be adduced of the ease with which some of the interesting operations of nature can be witnessed in the portion of creation now under our consideration, and amply repay us for the trouble. It is afforded by the humble, persecuted, but most beautiful of our native molluscs, the snail, (Helix nemoralis,) the little creature we barbarously crush beneath our feet, considering it a common enemy to horticulture. When we examine its wonderful formation, its tenacity of life, its reproductive powers, an instructive lesson may be furnished to the conchological student, most satisfactorily explaining the growth of the vast proportion of similarly constructed shells in other genera, and enabling him to understand by actual observation, and the evidence of his own reason, some of nature's steps in this branch of her works; he may easily watch the various changes that take place from the slight viscous covering with which the animal's body, in the first instance, is coated, or, as it were, merely glazed, till that substance becomes a consistent firm shell, finally fashioned into a painted palace adapted to the form and use of its inhabitant. It needs no logick to prove, that wherever creatures are endowed with a long endurance of life and great reproductive powers, great purposes are assigned to them. The contemned snail does not, therefore, merit the ill treatment it constantly experiences from man; and if we for a moment reflect upon its good services, and overlook its bad ones, we are bound to confess the former greatly outweigh the latter. It is viewed as a destructive marauder in our trim gardens; but we forget that we have invited its inroads by placing, within a comparatively limited space, a choice selection of dainty food even to the pampered appetite of man, but altogether irresistible to a snail. In the open fields, or the widely expanded forest, this little creature performs useful purposes in conformity to the ends of its creation; one of the most important of which is that of assisting in consuming the exuberant productions of nature, which, without its operations, would encumber the surface of the globe, check the progress of fu ture vegetation, and interrupt that perpetual harmony of system, which has wisely ordained that the extinction of life shall nct be felt, but its devastations HAMBURGH is one of the most considerable of the become supplied by succeeding generations, each of free cities of Germany; it is situated about eighty their kind, whether vegetable or animal. In coun- miles from the mouth of the Elbe, upon the northern AMERICAN COMMERCE. HAMBURGH. bank of the river, which is navigable for large vessels as far as this port. The circuit of the city is about twenty-two thousand feet. In the northern part is a lake, formed by the small river Alster, which runs through the city into the Elbe, and turns several mills. An arm of the Elbe enters the city from the east, and is there divided into a number of canals, which take various directions, till they unite, end join the Alster in the southern part of the city, where they form a deep harbour for ships, which communicates with the main branch of the river; and there is a large space enclosed by strong piles, where ships may lie in safety; which is called Rummelhaven. val of the old fortification was commenced ir 1804, and the great French works have also been since demolished. The established religion in this city is the Lu theran, but complete toleration prevails. The manners of the inhabitans resemble those of the other mercantile cities of Germany or Holland; publick worship is regularly attended, industry is generally diffused, and good morals prevail. Foreigners have long been freely admitted to reside in the town; and the troubles of the French revolution brought to it individuals of different nations and characters, all of whom were allowed to remain as long as the publick tranquillity was not disturbed: hence the variCanals intersect the lower part of the city in all ous and sometimes contradictory accounts of the directions, and almost all the warehouses are built morality of the place. The favourite taste of the upon their banks. In this part of the city, and also inhabitants, in point of amusement, is musick; and in that which lies on the east of the Alster, the previous to 1807, the era of commercial misfortune streets are, for the most part, narrow and crooked. to Hamburgh, the higher class of merchants lived Many, however, of those in the western or New not only with hospitality, but with a certain degree Town, are broader and straighter. The church of of luxury. Hamburgh has long been distinguished St. Michael, with its tower, four hundred and fifty- as a commercial city of the first importance. Its six feet in height, built by Sonnin, and intended for transactions consist partly in agency, but more in astronomical observations and for experiments in the purchase and sale of goods on account of its natural philosophy, was finished in 1786. This merchants. They buy the commodities of America. building, and some of the private houses, are re- Great Britain, France, Spain, Portugal, Holland, markable for their architecture. The exteriours of Belgium, the West Indies, &c., and supply with the exchange and the council-house are also hand-these all the countries lying along the Elbe, differsomely ornamented. Among the most remarkable ent districts on the Rhine and Lower Maine, and a buildings are the bank, the admiralty buildings, the part of the Prussian and Austrian dominions. They orphan asylum, the new general hospital, the thea-also buy up the products of these countries, of tres, the exchange, the city and commercial libraries, Röding's museum, &c. The gymnasium and the Johanneum are excellent institutions for education. The building for the school of navigation, opened in 1826, is provided with an observatory, and a botanick garden is also annexed to it. meat, mineral products, iron wares, in short all the products of the northeast of Germany, and a great part of those of the centre and south. This trade, like that in foreign goods, is carried on, partly on commission, partly for account of the Hamburgh merchants. which linen and thread are the chief. These articles are brought in great quantities from Bohemia Moravia, Lower Saxony, and Westphalia, and the inhabitants of these retired quarters have discovered, that to make sales through the medium of Hamburgh is less hazardous than direct intercourse with the In institutions for the relief of the destitute, for countries where their commodities finally arrive. the sick, and for the education of poor children, The trade in timber is also of great importance, esHamburgh is inferiour to no city in Germany. Most pecially during a maritime war, Hamburgh being the of these are under the direction of private individu- chief medium between the Baltick and the south of als, and they are principally supported by voluntary Europe. The other articles of trade are very various, contributions. The constitution of Hamburgh is comprising flax, hemp, potash, tar, tobacco, wax, aristocratick. The government consists of four bur-honey, hides, wool, woollen yarn, smoked and salt gomasters and twenty-four councillors. To the senate are attached four syndics and four secretaries. Calvinists are excluded from the government of Hamburgh, as Lutherans are from that of Bremen. The ordinary publick business, both internal and external, is transacted by the senate alone; matters of more importance are regulated in connexion with the citizens possessed of a certain property. These are divided into five parishes, each of which sends thirty-six members to the assembly or general college. From these are chosen the members of the council of sixty, and again from these fifteen elders. Each of these colleges has peculiar privileges. The senate and the elders alone receive salaries. Justice is administered by several courts. But the court of appeal of the free cities of the Germanick confederis the superiour tribunal. The publick revenues were formerly considerable, without the taxes being oppressive; but the heavy debts incurred by the city, of late years, have greatly increased the taxes. The citizens are provided with arms, and accustomed to military exercises, so as to form a body of infantry, cavalry, and artillery, in regular uniform, amounting to about ten thousand men. The remo acy The territory of Hamburgh, which contains one hundred and sixteen square miles, is bounded by that of Holstein on the north and west; the city of Altona, in the territory of Holstein, is not two miles distant from the gates of Hamburgh. Toward the east the Hamburgh territory borders on Lauenburg, and on the south it is separated by the Elbe from the territories of Hanover. Some of the islands in the Elbe belong also, either wholly or in part, to Hamburgh, together with the village of Moorburg on the left bank. Besides this, it has a jurisdiction over the bailiwick of Ritzebüttel, which contains the important town of Cuxhaven, at the mouth of the Elbe. Hamburgh, in common with Lubeck, also has jurisdiction over the bailiwick of Bergedorf, with the small town of the same name, over the Vierlands, and a few places in Lauenburgh. The city owes its foundation to the emperor Charlemagne, who, in |