quence only of its being at reft; though the progress of this coagulation is very flow. Article 33. On the Degree of Heat which coagulates the Lymph, and the Serum of the Blood; with an Enquiry into the Caufes of the inflammatory Cruft, or Size, as it is called. By the Same. From Experiments made on the blood of animals, confined within the veffels by ligatures, the Author concludes, that the human lymph probably coagulates in a heat between 114 and 120 degrees of Fahrenheit's thermometer; that the ferum requires a heat of 160 degrees to fix it; and that confequently the blood cannot be coagulated even by the moft morbid degree of animal heat, which never rifes above 112° in the most ardent fever. He next enquires into the origin and nature of the fize that frequently appears on the blood, though it is not always obferved, in inflammatory diforders; and, which is fometimes obferved, when no fuch diforders exift. His experiments tend to prove, that it is not formed from the ferum of the blood, but from the fixation of the coagulable lymph; from which the red particles have fpontaneously feparated, and fubfided, in confequence of their greater fpecific gravity. In treating this fubject, he controverts an opinion very generally adopted by medical writers and practitioners; who fuppofe that this fizey kind of blood is thicker and more coagulable than that which does not prefent this appearance; and that, in general, the blood is thickened in inflammatory diforders. From his experiments and obfervations it appears that, on the contrary, fizey blood coagulates much more flowly than other blood; that inflammation actually leffens the difpofition of that fluid to coagulate; and that, in inflammatory diforders, where this whitish cruft or fize appears, the blood, or at least the coagulable lymph which conftitutes this inflammatory fize, is really attenuated, For the particular experiments which render these opinions probable, we must refer our medical Readers to the article itself. Article 34. Further Remarks on the Properties of the coagulable Lymph on the topping of Hæmorrhages; and on the Effects of Cold upon the Blood. By the Same+. In this paper the Author confirms the reality, and undertakes to affign the cause, of certain appearances noticed by fome who have written on the blood, but never yet fatisfactorily accounted for. It has been obferved, in the operation of bleeding, that the blood which flows into the first cup fhall sometimes be Thefe three articles have lately been published, with additions by the Author, in a volume apart. See laft month's Review, page 251. covered covered with an inflammatory cruft; while that received into the subsequent cups exhibits no fuch appearance. The cause of this diverfity has been attributed to the greater or lefs velocity with which the blood flowed into the veffel, and to other local circumstances: but the Author has noticed this change in cafes where no difference of this kind, or in any other circumftance, was to be obferved; and where, for inftance, the blood in the first cup was covered with an inflammatory fize, and was late in coagulating; that, in the fecond, had a cruft only upon a part of its furface; and the third and fourth cups had no appearance of fize, and manifeftly coagulated before either of the other two. : The Author's folution of thefe remarkable appearances is, in fhort, this he is of opinion that thefe changes are not produced by any external circumftances; much lefs that they are owing to a kind of elective evacuation, if we may fo call it, of the vitiated part of the blood, on the first opening of a vein. He fuppofes, what will not be univerfally adopted by phyfiologifts, that, during the evacuation, that is, in the fhort space of five or fix minutes, the nature and properties of the entire mass of blood remaining within the body, or at leaft of the coagulable lymph, are actually changed; and that, in that time, an alteration is produced in that state of the blood-veffels, on which the thinnefs, and diminished tendency of the lymph to coagulation, depend. This fact, he obferves, renders it probable that this vitiated blood is not the cause of difeafe; fince the disease remains, though the properties of the blood are changed.'-But this reafoning is not perfectly conclusive: for, granting a total change to be thus fuddenly effected in the mafs of blood, by the evacuation of a part of it; many of the effects already produced by vitiated blood, and confequently the dif ease, may still remain, though the vitiated blood no longer exists. From the evidently increafed difpofition of the blood to coagulate the more quickly, in proportion as greater quantities have been taken away, the Author draws fome confequences relative to practice; particularly with regard to hemorrhages. But for thefe, and the experiments which follow, relating to the effects of cold upon the blood, from which it appears that cold retards or abfolutely prevents its coagulation, we must again refer to the original. t The 38th or laft article of this clafs contains the hiftory of a cafe fimilar in many refpects to that of the Cuticular Glove, defcribed in the preceding volume of the Tranfactions. CHEMISTRY, ELECTRICITY, and METEORS. Article 19, Experiments and Obfervations on Charcoal. By Jofeph Priestley, LL.D. F. R. S. The chemical properties of this fubftance are not so much the fubject of this article, as those variations in the process by which it is made; by an attention to which, the Author imagined, fome light might be thrown on the caufe of the very great differences obfervable in the conducting power of different pieces of charcoal, and poffibly on the nature of the conducting principle itself. He was formerly induced, by a very plausible analogy, to fufpect that it refided in the inflammable principle, or me phitic air, contained in bodies, united with an earthy or other bafis. With respect to this circumftance, metals and charcoal exactly agree. While they retain their phlogiston; they both conduct; but when deprived of it, they lofe that quality. Water, however, furnishes a ftrong exception to the univerfa lity of this propofition. Among other confiderations he was led to this fuppofition, by the perfect conducting power, which he first discovered in charcoal; a fubftance which, on other accounts, appeared very unlikely to be poffeffed of it. Wood, in its different ftates, exhibits a fingular variety in its electrical properties. In its common ftate, it is a non-electric, or a conductor being fubjected to a moderate degree of heat, or baked, it becomes an electric, or a non-conductor; but, on -being expofed, in a particular manner, to an intense heat, or charred, it returns to a non-electric ftate, and becomes one of the most perfect conductors; in no refpect inferior, with regard to this quality, to gold, filver, or the moft perfect metals. From the experiments now before us it is evident, that charcoal owes this remarkable quality to the degree of heat that is applied in the process of making it. It appears likewife, that this quality is improved in proportion to the intenfeness of that heat. Pieces of wood, which had been coaled flowly, or in a moderate fire, in which they were kept a long time till they were black quite through, fo as not to be diftinguished from the most perfect charcoal, were repeatedly found, not merely, as might be expected, to conduct lefs than other charcoal; but not to conduct in the leaft degree. With regard to the manner in which heat effects this change, a variety of circumftances lead the Author to conclude, that the cause of blacknefs, and of the conducting power in charcoal, is the oil of the plant rendered empyreumatic, and burnt to a certain degree;' and that these properties are fome way connected with that part of the phlogiftan or the inflammable principle, the escape of which is prevented in the process of charring, and the fixation, and union of which with its bafis, the earth of the plant, is ftrengthened by an intenfe heat. This opinion is in part confirmed from hence; that the very fand or pipe-clay, with which the Author covered the fubftances that were to be converted into coals, contracted, from the phlogiston expelled from thefe fubftances, a blacknefs like that of charcoal, and acquired a conducting power; which might afterwards be improved, by expofing them in a clofe veffel to a ftill greater degree of heat, Article 18. An Investigation of the lateral Explosion, and of the Electricity communicated to the electric Circuit, in a Difcharge. By the Same. The fingular refults of the experiments related in this article may furnish the experimental philofopher with a very useful leffon; not to be too hafty in eftablishing general laws.. Hitherto all electricians, we believe, would have concurred in affirming, that whenever an electric fpark appears between two bodies, each of them fingly is either receiving, or parting with, a certain portion of electric matter. But it is evident from thefe experiments, that a full, ftrong, and bright fpark, fometimes more than an inch in length, may be produced between two bodies, which does not communicate any electricity to, or take any from, the body which appears to receive or part from it. We fhall content ourselves with giving a fhort defcription of the best manner of performing this remarkable experiment; fo that the fpark may be obferved to the most advantage, and its incommunicative property may, at the fame time, be compleatly ascertained. Let a charged jar ftand upon a table, and one end of an infulated thick brafs rod be placed contiguous to its outward coating. Near the other extremity of this rod the body is to be placed that is to receive the fpark; and which, we fcarce need to add, should be infulated likewife, in order to afcertain the confequences of the experiment. This body fhould be fix or feven feet in length, and perhaps fome inches in thickness, or be connected with a body of thefe dimenfions. The jar is to be difcharged with a rod refting upon the table, close to a chain, the extremity of which ought not to touch the coating of the jar, but fhould reach within about an inch and a half of it. We pass over the reafons which require this difpofition of the apparatus, and proceed to add, that, at the inftant of discharging the jar through this interrupted circuit, the operator will hardly fail of getting a fpark or lateral explofion, an inch in length; which will appear between the firft mentioned rod and the infulated body. At the fame time, the latter will fhew no figns of having either received or loft the most minute portion of electrical matter by this ftrong spark; as, even at the time of the explosion, there is not the leaft motion given to the lighteft pithballs, or the fineft threads fufpended from it. We Y 4 refor refer the Reader to the article itself for an account of the manner in which the Author was led to discover, that, in this cafe, the electric fluid fuddenly enters, and, as to fenfe, inftantaneoufly leaves the infulated body, without making any fenfible alteration in the electricity natural to it. Article 25. De Atmofphæra electrica, Joannis Baptiftæ Beccariæ, R. S. S. ex Scholis piis, ad Regiam Londinenfem Societatem Libellus. By the feries of experiments contained in this paper, one of the most fingular and important properties of the electric fluid, fucceffively obferved and explained by Mr. Canton, Dr. Franklin, and Meffrs. Wilke and Epinus, is completely and} fatisfactorily demonftrated. This law, which throws fuch light on the properties of the electrical fluid, and on the phenomena of the Leyden Vial in particular, is, that the electric matter being accumulated in any body, repels that naturally exifting in other bodies in its neighbourhood, and thereby renders them negatively electrical: and this effect it produces, although fubftances intervene through which the electric fluid itself does not pafs. Indeed, all our experiments concur in afcertaining this fingular fact; that though glafs, air, and other non-conducting fubftances, are impermeable to the electric matter itself, yet they are pervious to the action of that fluid; either by means of fome vibration, or other peculiar modification of their own particles, or by the intervention and agency of fome fubtile and unknown medium. When we fay that the electric fluid, condenfed on one fide of a plate of glafs, repels that which naturally belongs to the oppofite furface, though itself is incapable of paffing through the fubftance of the glafs; we do not mean that the electric, or any other matter, can immediately act on other matier in diflans, or where it is not: for that would be abfurd. The impermeability of the glafs, and the repellent power of the electric fluid through it appear to be matters of fact, fatisfactorily established by experiment; and it is the bufinefs of philofophers to difcover the particular means or media, by which its action is communicated through bodies, which refift its actual paffage through them. The greater part of the experiments, contained in this dif fertation, prove this property of the electric fluid, as exerted through air; and particularly, that one furface of a plate of air cannot receive an additional quantity of electric matter, unless a paffage is given for the efcape of the natural electricity of the contiguous frata into the earth. We fhallbriefly defcribe one of thefe experiments. The Author electrifies, pofitively, for exmaple, a hollow metal cylinder, which he terms the electrical well, Into this he lets down another fmaller cylinder, completely infulated, which he calls the bucket. We should obferve, that it |