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Up cheeks for the more ready receiving of any rope ; as by thisnotch tiie middle part of a rope may be received into the blockwithout passing it endwise, it is commonly fastened with a strapabout tlie mainmast, close to the upper-deck, and is ohiclly usedfur the fall of the winding tackle, w hich is reeved into this block,and then brought to the capstan.

Block-House, a kind of wooden fort or battery, either mount-ed on rollers or on a vessel, and serving either on the water orin counterscarps and counter-approaches. The name is some-times also given to a brick or stone fort built on a bridge, or thebrink of a river, serving not only for its defence but for thecommand of the river belli above and below : such was that notedblock-house anciently on the bridge of Dresden , since demolishedon enlarging the bridge.

BLOCKADE, in the art of war, the blocking lip ofa place, byposting troops at all the avenues leading to it, to keep suppliesof men ami provisions from getting into it ; and by these meansproposing to starve it out, without making any regular attacks.

Blockade, to raise a, is to force the troops that keep theplace blocked up from their posts.

Block-Battery, in the military art, denotes a wooden batteryon four wheels, moveable from place to place, whereby to tire enbarbe, or ever the parapet; sometimes also used in galleries andcasemates, ‘where room is wanted.

BLOCKY, among jewellers, an epithet given to a diamondwhen its sides are loo upright, by its table and collet being toolarge.

BLOEMEN, Peter Van, a celebrated painter, born at Ant-werp . As soon as he found himself competently skilled in colour-ing, penciling and designing, he returned to his native citv, vliere,in 1699, he was appointed director of the academy, flis com-position is rich, and his pictures are generally tilled with a numberof figures. Ilis subjects are, squadrons of cavalry, eucimp-ments, artillery, battles, Italian fairs, markets, and festivals; inw hich he shewed great correctness in drawing, and an elegancein the manner of dressing his figures; whom lie frequently re-presented in drawing, and an elegance in the manner of dressinghis ligures ; whom he frequently represented in oriental habits,lie designed horses in an admirable style ; and in Ids battles gavethem anmidance of spirit, graceful attitudes, and an expressionfull of life. Ilis landscapes are enriched with elegant architec-ture, with basso-relievos, and mutilated statutes, in a line taste ;and rendered still more pleasing by a good colour, by animals ofdifferent kinds, and excellent figures.—His best works are admi-red in all parts of Europe , and afford large prices: but someof his pictures seem rather too much laboured, and these are pro-portionably less valued.

BLOIS, a town of France, in the department of Loire andCher, SO miles S. W. of Versailles . Lon. 1. 25. L. Lat. 47.35. N.

BLOMAUY, the first forge in the iron mills, through whichthe metal passes, after it lias been first melted from the mine.

BLOXDEL, David, a protestant minister, distinguished byhis skill in ecclesiastical and civil history, was born at ChalonsMir Marne, and admitted minister at a synod of the Isle of France ,in 1614. He was afterwards made an honorary professor with asuitable pension, by the national synod of Charenton. On thedeath of Vossius, lie was chosen professor of history in Amster-dam , vvliifl er lie went in 1050. He wrote, 1. A Defence of theReformed Churches of France . This was in answer to the bishopof Lusson, afterwards the celebrated cardinal Richelieu. 2. Awork against the Decretal Epistles. 3. De Episcopis et Presb-y-teris. 4. Pseudo Isidores. 5. A Treatise of the Sy bils, whereinhe proves their oracles false. 6. A Treatise concerning PopeJoan, wherein lie offended some of his Protestant friends, by dis-crediting the story of the female pope. 7. De Formula RegnanteChristo. 3. Considerations rcligieux et politiques; on the warbetween the republics of England and Holland; and some otherpieces. Bayle informs us tiiat “ lie had a singular way of study-ing ; lie lay on the four, and had round about him the neces-? rv books lor the work lie had in hand.” He died in 1655,aged 64.

' Blo.nDei, Francis, regius professor of mathematics and ar-chitecture, was employed in several negocialions, arrived at theiigcdv of marshal de camp and counsellor of stale, and was ap-

pointed to teach the dauphin mathematics; he was also mademember of the Academy ot Sciences at Paris , and director of lireAcademy of Architecture. lie died at Paris in 1680, aged 68.He wrote, 1. Votes on Suvut’s Architecture. 2. A Course ofArchitecture. 3. A Course of Mathematics. 4. The Art ofthrowing Bombs. 5. A New Manner of fortifying Places. 6. AComparison between Pindar and Horace. 7. A History of theRoman Calendar, &.e.

BLOOD, Sanguis, the most copious fluid in the animal Iiodv,and essentially necessary to the preservation of life : it is generallyof a red, but in most insects, and in all worms, of a w bile colour.It lias a considerable degree of consistency, and an unctuous feel,as if it contained a quantity of soap. Its taste is slightly saline,and it lias a peculiar smell. The human body is, by Dr. Keil,supposed to contain at least one-half of its weight in blood ; in-cluding in this compulation all that exists in the lymphatic dm C,nerves, or any other vessel. This computation, however, is ex-aggerated ; and we believe that the greatest quantity in a full—grown adult, seldom exceeds thirty pounds weight. Its most re-markable property is that of incessantly circulating in the cavitiesof the heart, arteries, and veins, while the animal is alive. Al-though Hippocrates appears to have possessed a faint idea of thisadmirable process, when he says, “ tiiat all the blood-vesselsspring from one ; and that this one lias neither beginning nor end ;for where there is a circle, there can be no beginning:” yet as hewas not acquainted with the ofiice of the valves, he could' neithercomprehend nor demonstrate, the circulation ot the blood. Thismost important of all discoveries in physiology, was reserved forthe immortal llarvev, who first ascertained the true nature anduses of the valves, and about the year 1616, taught, in his Lec-tures at Cambridge, that justly admired doctrine, the substance ofwhich he published in 1628. He proved that, in most animals,the blood circulates in arteries and veins, and through the me-dium of one, two, or more hearts ; that in arteries it moves fromtire trunk to the branches; and that, meeting there with thebranches of veins, it returns in a languid state to the heart ; thatthe heart communicates a new impulse, and propels it to the trunkof the arteries; and that by these, the thickness of their coals, ex-erting muscular force, again drive it into the veins. Valves aresituated in every part of this circulating course, in order to pre-vent the return ol the blood. The colour of this fluid in the arteriesis of a florid hue; but somewhat darker in the veins, except inthose of tlie lungs, in which it is of a lighter cast. When exposedto the opeu air, tlie blood gradually separates into two parts,namely , the serum, or a yellowish, sometimes greenish lluid, andthe erassamentum, coagulum, or cake, which resembles a redmass swimming distinctly on the top. The latter contracts greatlyin its dimensions, and increases in solidity ; properties which de-pend on tlie state of tlie individual at tlie time when the blood isdrawn. Hence, in vigorous persons, when attacked with an in-flammatory disease, tlie solid part is so tough that it resembles apiece of ilesh, and lias therefore been called tlie bully coat;whereas, in other diseases, it is very soft and tender, breaking inpieces on the slightest touch. By chemical analysts, it discoversnine principal parts, 1. The aroma spiritus rector, or odorouspart; it very sensibly affects the smell, is volatile, and soluble inwater and alcohol. 2. The fibrin, or fibrous matter the principalsource of its vitality, nutriment of the muscular fibre. 3. 'I In;gelatin, or jelly, found in the serum alone. 4. Tlie albumen,common to tlie coagulum and serum. 5. The red part. 6. Ironwhich some suppose the basis of the red part, but this admits ofmuch doubt. 7. Sulphur. 8. Alkali, or soda ; and 9. Waterexisting in a great proportion, yielding in distillation a volatile spi-rit, a great quantity of phlegm, and fetid oil; lastly, there remainsa charred matter, which, when burnt in the open air, leaves aw hiteartli similar to calcined hartshorn. According to some chemists,however, it contains both an acid and an alkali. But the most re-markable circumstance in the blood, is its texture, which consistsof millions of red globular particles, or more properly, as Mr.

I lew son calls them, fiat vesicles, each of winch has a little solidsphere in its centre. He observes, that they are flat in all animal ■,of very different sizes in different creatures, and impart to tin;blood its red colour. Inman, they are small, perfectly tlat, an lappear to have a dark spot in tlie middle. To see them distinctly,he diluted tlie blood with fresli serum. Their shape he supp< sedto be of great importance, bill it can be altered w ith a mixture of

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