Page:Encyclopædia Britannica, Ninth Edition, v. 3.djvu/851

Rh 1em 1em 1em  BLOCH,, a German naturalist, born at Ansbach, of very poor Jewish parents, about the year 1730. Having entered the employment of a surgeon at Hamburg, he was enabled by his own exertions to supply the want of early education, and made great progress in the study of anatomy, as well as in the other departments of medical science. After taking his degree as doctor at Frankfort-on-the-Oder he established himself as a physician at Berlin, and found means to collect there a valuable museum of objects from all the three kingdoms of nature, as well as an extensive library. His first work of import ance was an essay on the different species of worms found in the bodies of other animals, which gained the prize offered by the Academy of Copenhagen. Many of his papers on different subjects of natural history, comparative anatomy, and physiology, were published in the collections of the various academies of Germany, Holland, and Russia, particularly in that of the Friendly Society of Naturalists at Berlin. But his greatest work was his Allgemeine Naturgeschichte der Fische (12 vols., 1782-95), which occupied the labour of a considerable portion of his life, and is considered to have laid the foundations of the science of ichthyology. The publication was encouraged by a large subscription, and it passed rapidly through five editions in German and in French. Bloch made little or no alteration in the systematic arrangement of Artedi and Linnaeus, although he was disposed to introduce into the classification some modifications depending on the struc ture of the gills, especially on the presence or absence of a fifth gill, without a bony arch. To the number of genera before established he found it necessary to add nineteen new ones; and he described 176 new species, many of them inhabitants of the remotest parts of the ocean, and by the brilliancy of their colours, or the singularity of their forms, as much objects of popular admiration as of scientific curiosity. In 1797 he paid a visit to Paris, in order to examine the large collections of such subjects of natural history as had been inaccessible to him on the shores of the Baltic ; and he returned to Berlin by way of Holland. His health, which had hitherto been unimpaired, began now to decline. He went to Carlsbad for its recovery, but his constitution was exhausted, and he died there on the 6th of August 1799.  BLOCK MACHINERY. A block is a case with its con tained pulley or pulleys, by means of which weighty objects are hoisted or lowered with facility. There is nothing in the appearance of a block which, to an unpractised eye, would seem to require any stretch of mental ingenuity or of manual dexterity to manufacture. It is a machine appar ently so rude in its structure, and so simple in its con trivance, that the name was probably given to it from its general resemblance to a log or wood, as is obviously the case with a butcher s block, a barber s block, the block of the executioner, &c. Of the two constituent parts of a ship s block, the external shell and the internal sheave, every carpenter might make the one, and every turner the other; but still block-making is a separate branch of trade, and it is necessary that it should be, for the whole effici ency of the block depends upon the proper proportions being observed between the various parts and the accuracy with which they are adjusted. Mr Walter Taylor of Southampton took out a patent in the year 1781, to secure the benefit of some improvement he had made in the construction of the sheaves. He also shaped the shells, cut the timber, &c., by machinery driven by water, and carried on so extensive a manufacture of blocks as to be able to contract for nearly the whole supply of blocks and blockmakers wares required for the use of the Royal Navy. Mr Dunsterville of Plymouth had a similar set of machines wrought by horse-power. Both his blocks and Taylor s were said to be superior to those constructed by the hand, though still deficient in many respects. It would appear that it was the enormous quantity of blocks consumed in the course of a long protracted war that first called the attention of the Admiralty or Navy Board to the possibility of some reduction being made in the expense of so important an article, and to the impru dence of depending entirely on a single contractor. On these considerations, it seems to have been the intention of Government to introduce, among other improvements in Portsmouth Dockyard about 1801, a set of machines for making blocks there. About this time, too, Mr Brunei had completed a working model of certain machines for con structing, by an improved method, the shells and sheaves of blocks. This model was submitted to the inspection of the lords commissioners of the Admiralty, and it was decided to adopt Mr Brunei s more ingenious machinery. The advantages to be gained were those common to all cases in which machine work supersedes hand labour, and consisted in the fact that, after the proper sizes of each part had been determined by careful calculation and ex perience, the machine could be made to observe these sizes with unerring accuracy, and so avoid all variations due to the carelessness or ignorance of the workman ; these con siderations are in blocks, perhaps more than in most things, of the utmost importance. Another advantage was, that the blocks could be made by Brunei s machinery about 30 per cent, cheaper than hand-made blocks had been previ ously obtained by contract, and the importance of this to the Admiralty in those days, when all ships were so heavily rigged, having no steam to supplement their sail power, will be sufficiently seen when it is stated that the remunera tion which Brunei was to receive for his invention was agreed to be the savings of one year, and that these savings were estimated at 16, 621; in addition to this he received an allowance of a guinea a day for about six years while engaged on the work, and was paid 1000 for his working model the total amount paid to Brunei for the invention amounting to about 20,000. The process may be described as follows : Pieces of wood are cut roughly to the size of the block, and the first operation is then performed by the lonng-machine, which bores a hole for the pin, and one, two, or three holes, as the case may be, for single, double, or treble blocks, to receive the first stroke of the mortising chisel; the block is next taken to the mortising-machine, where the mortise or mortises for the sheaves are cut ; after this, to a circular saw, conveniently arranged for cutting off the corners and so preparing the block for the shaping-machine, which con sists principally of two equal and parallel circular wheels 