if they be perused with caution as coming from a declared partifan, and an accufer of the men whose measures he condemns. We think that it would be of great ufe to the noble Lord, if he would endeavour to speak with the fame temper with which he writes; he would then find his auditors more attentive, and his arguments infinitely more impreffive. We truft that he will not be offended with us for this advice, nor pronounce it to be officious and ill-timed; we really mean it in good part; and we are perfuaded that, if he can bring himself to adopt it, he will derive no fmall advantage from it. At the fame time we are aware that, though he should be difpofed to take the hint, he will not find it easy to get rid, in a short period, of a habit of long standing. The word preventative, which is not English, occurs too often to warrant us in confidering it as an error of the prefs; and it is not to be found among the errata. It is too generally used for preventive, even among thofe whofe education ought to make them explode it. Medical writers, we think, are more chargeable with this base coinage than any other class of literary men. ART. XII. Lectures on Electricity. By G. C. Morgan. MR. Morgan attributes the conducting quality of charcoal, as diftinguished from baked wood, to the innumerable minute cells or cavities which it contains, and which, in his judgment, must be very favourable to the paffage of a fluid equally fubtile with that of electricity *.' A little attention will difcover the fallacy of this appeal to the fenfes. Were the argument juft, it would follow that powdery fubftances conduct better than folid. If the cavities be filled with air, they will have fome influence in retarding the tranfmiffion of electricity, fince air is widely removed from the character of a conductor. On the contrary, if they be perfectly void, their counteracting effect will be still greater, because experiment afcertains that an electric difcharge cannot be made through a vacuum.-When woad is converted into charcoal, it undergoes a total change of properties. The principle which Mr. Morgan lays down, in p. 166, vol. ii. feems to be of an opposite kind. The refiftance of all fubftances to the paffage of the electric fluid increases with the distance from each other by the removal of preffure, or by the influence of any repellent power.' That, with certain limitations and exceptions, the rare fubftances are imperfect con ductors, we would admit:-but what idea can be formed of refiftance which is leaft when the conducting medium is denfe ? Here is a notable inftance of the inaccurate and undefined application of that term in the science of electricity. Resistance in mechanics denotes a conftant retarding force, which is proportional to fome function of the velocity. The electricians appear to fignify by it the vague conception of an obstacle to be overcome before the motion commences. Mr. Morgan endeavours to account for the diverfities of conducting power in different bodies, by a theoretical application of the doctrine of attraction. The multiplied fuppofitions which he employs leave on the mind a very indiftinct and unfatisfactory impreffion. Even granting the ample conceffions which he would require, it appears difficult, if not impoffible, to arrive at accurate conclufions. The author fhews much subtlety, however, in his attempt to explain the manner in which the electric fluid operates when folid electrics are broken by the explosion. A musket-ball, it is obferved, will pierce through a board delicately fufpended, and not caufe the fmalleft change of pofition; because the motion of the ball is fo rapid as to fpend itself on the fpot ftricken, without being communicated to the other parts of the board. Brittle fubftances, fuch as glafs and rofin, derive their character, according to Mr. Morgan, from the flownefs with which they tranfmit an impulfe through their internal ftructure. Hence, if the electric fluid, darting with inconceivable rapidity, encounters these fubftances, its ftroke will be partial, and will confequently produce a difruption. The idea is plaufible and ingenious, but confined in its application. An explofion of electricity never makes a clean perforation; it fhivers hard fubftances, and raises protuberances on fuch as are foft. When opposite wires are inferted in a glafs tube containing oil, the tranfmiffion of a charge caufes a general difperfion. In vain fhall we attribute the effect in this inftance to the difficulty with which the electric fluid obtains a paffage; for the violence is greatest when the tube is narrow, and when the ends of the wires are near to each other. Having difcuffed the theoretical principles of electricity, Mr. Morgan next applies them to explain the natural phænomena of our atmosphere; and, in this part of the work, we find more demands on us for praife. With few exceptions, it contains unquestionably the most accurate and complete view of the fubject that has yet appeared.-He will hardly admit that lightning ever ftrikes the ground, and thinks himself warranted to affert that ninety-nine thunder-claps out of one hundred are nothing more than the harmless discharge of one cloud into another.' Into this fingular opinion he is led by his theory of conductors already already noticed.-The manner in which he accounts for the prolonged noise of thunder is very fatisfactory. All founds formed at a diftance ftrike the ear with fucceffive reverbe rations; for each confiderable object becomes the centre of aërial undulations. Mr. Morgan very properly imputes the mortal or flunning effects of lightning to its operation on the nervous fyftem. The recent experiments on animal electricity countenance this opinion; and we can inform the public that Dr. Van Marum of Haerlem has now put the queftion beyond doubt. This celebrated electrician employed eels and other animals of cold blood, which are capable of being ftimulated into contractions for fome time after death. On fending the charge of his great battery through portions of their bodies, the power of irritation was inftantly deftroyed.-To the fame principle must be referred the effects obferved by Mr. Morgan. A large fhock of electricity confined to the head caufes momentary forgetfulnefs, impairs the fight, and produces head-ache, followed by a depreffion of fpirits and a general proftration of ftrength. If the diaphragm be brought into the circuit of a discharge, the perfon will fhout aloud; or, if the ftroke be smaller, it will excite a violent fit of laughter. A fhock fent through the bladder, or rectum, convulfes the fphincter muscles, and occafions immediate evacuations. Mr. Morgan combats the important theory of Lord Stanhope concerning the returning ftroke. His objections reft all their force on the validity of the peculiar opinions advanced in the foregoing parts of the work: we cannot therefore acquiefce in the conclufions. The fcepticism, with refpect to certain facts urged in confirmation of that theory, appears to be fomewhat unreasonable. Perhaps the ingenious nobleman over-rates the effects of his principle, but it is certainly just in the main, and of moft comprehenfive application. Mr. Morgan's obfervations on the figns which precede thunder-ftorms, and on the precautions to be used in such cases, are clear and judicious. He has no great faith in the protection afforded by conducting-rods of the ordinary conftruction. To avoid all poffible danger, he directs that, when a house is built, ftrips of lead should rise on each fide and communicate with the water-pipes, and with other ftrips laid under the foundations of the partition walls. The expence would not be exceffive. The fame plan may be extended to fhips, where chains have been very injudiciously employed. One strip of metal fhould furround the deck, another fhould be faftened to the bottom or the fide of the keel, and ftrips connected with these should run along the stays to guard the mafts. We will add that, with the fame dimenfions, copper for a conductor is greatly preferable to lead. Mr. M.'s account of the origin of natural electricity is fo interefting, that our readers, we are confident, will be gratified by the following extracts: By Mr. Bennet's electrofcope, we are taught that whenever a folution or precipitation takes place, or whenever any two bodies, having a mutual attraction to each other, are united or separated, a change, attended by electrical figns, is immediately produced. This is particularly the cafe in air, and the change is never fo confiderable as when its component quantity of moisture is either increased or depofited. In our endeavours, then, to explain the production of natural electricity, we have nothing more to do, than to discover the various circumitances of the atmosphere, nothing more to do than to discover the various circumstances in which moisture is abforbed or precipitated. When these are known, it can be no difficult business to find out the feveral partial and lefs powerful caufes which may either increafe or diminish the effects of the general and moft powerful caufe. It is, however, previously neceffary to remind you of the proof furnished by numerous experiments, that when any portion of the atmosphere is in a state to take up an additional quantity of moifture, it is in a state at the fame time to take up more electric fluid; and, vice verfa, when it is parting with its water, it is at the fame time parting with its electric fluid. But in thefe cafes neither the fuperabundance nor the deficiency can produce a charge, unless there be fome other part of the air contemporaneously in an opposite state, or in a difpofition either to receive or give. It is, however, fcarcely poffible that this fhould not always happen; for our atmosphere is, throughout its vaft dimenfions, each moment agitated by millions of co-inftantaneous changes, and for our purpofe it is of no confequence where the required change takes place. Were it in New Holland, or at the Antipodes, a connexion would be inftantly formed between the remote but oppofite fituations, by the conducting power of the earth. It is a neceffary conclufion, from what I have just faid, that if the abforption of moisture by the air, or the copious evaporation of it from the earth, be attended with a new accumulation of the fluid; then where this caufe operates moft powerfully, there its correfpondent effect will be moft fenfible. We confequently find, that the moft tremendous electrical phoenomena belong to the countries within the Tropics, or to that portion of our atmosphere which is loaded with moisture by the most powerful influence of the fun's rays. In like manner, within the limits of our own and other fimilar climates, electrical phænomena are greatest, both in force and frequency, during the hottest months of the year, or during the feafon in which our at mofphere is moft copiously and rapidly charged, by absorbing the humidity of the ground. In the neighbourhood of Etna and Vefuvius, during the period of their volcanic fury, furfaces, covering the dimenfions of feveral fquare leagues, are fometimes fcorched with red hot lava, and every atom atom of their moisture is rapidly diffipated. At the fame time the furrounding air is heated to a vaft extent, and in this state swallows up an immenfe quantity of aqueous vapour; but contemporaneously with the operation of thefe powers, according to the reports of all natural hiftorians, an immenfe quantity of the electric fluid is accumulated and difcharged. Again, a dry wind, paffing over a moist foil, is another modification of the caufe we are applying: it produces a copious and rapid folution of aqueous particles, and its confequent alteration of attractive force. Let us, for instance, fuppofe a wind, which had passed over the deferts of Arabia, or that had been well roafted in its paffage over a large extent of burning fands, to come in contact with a fimilar extent of marthy foil, or of any furface well drenched with water, a most abundant evaporation would neceffarily take place, and with it an immenfe accumulation of the electric fluid. But fubfequently, in cafe any power operated, which would take away the aqueous particles thus diffolved, and of course altered the degree of attractive force by which the collected electric fluid is fufpended, we should find that the most dreadful thunder-ftorms would take place. This is really the cafe; for there is fcarcely a region in the val circle furrounding the immeafurable fands of Africa, which is not remarkable for ftorms and tempefts. On the side of Abyffinia, when the warm winds that have paffed over the neighbouring deferts are condenfed on its mountains, thofe deluges are collected which form the inundations of the Nile. On the coast of Guinea, the harmattan, which is a current of air fo dry as to wither and pulverize, by a complete abforption of all its juices, every fubftance that occurs in its paffage, is no fooner mixed with that body of air which is cooled by the ocean, than it forms the moft terrific hurricanes of wind and lightning that are described by navigators. Along the Syrian regions, we learn from facred authority, that the ftorms gather with fuch rapidity, that a cloud which the hand might cover this inftant, is within the interval of a few minutes charged with water adequate to the inundation of a whole country. The thunder that attended thefe impetuous ftorms, provoked the fublimeft expreffions of their poets. Indeed, whenever their minds attempt the defcription of celeflial greatnefs, or the fudden and overwhelming approach of divine power in its triumph or in its fury, they have recourfe for imagery to thofe thunder-clouds, which they juftly reprefented as extinguishing the light of the fun, and as involving the world in a few inftants in the darkness of midnight.' Dr. Hutton's ingenious theory of rain is happily applied by Mr. Morgan: In tropical climates, day follows day for months together, in which the calm atmosphere becomes loaded by one addition of moifture to another, till it becomes at last the reservoir of vast rivers and lakes, and of all the moisture that is fpread over whole continents. But when this drought has reached its crifis, the fun paffes the line, the wind takes a new direction, a colder air mixes with that which is thus charged with vapours, and the condenfation becomes fo copious as |