diately on their recovery from this torpid state, but continue quiet till they have consumed the remains of their provisions, which amounts often to one-third of the whole: then, the former opening his hole in March, the latter in April, they come out, return to their former manner of life, and go about seeking herbs. "It cannot be denied, that the hamster is a very destructive creature. Some years they are so numerous as to occasion a dearth by their immense comsumption of corn. In one year 11,000 skins, in a second 54,000, and in a third 80,000, were brought to the town-house of Gotha, to receive a reward for their destruc tion. The hamster lives a consider able time, and multiplies prodigious ly. The female brings forth twice or thrice in the year, and her litter is never fewer than six; but oftener from sixteen to eighteen. The growth of the young is very rapid: at fifteen days old they begin to dig the earth; and in about three weeks they are capable of subsisting independently of the dam. tained no damage; so that instead of blaming the Divine Government, we shall have much reason to adore it. After all, what are the few pounds of corn which the hamster carries away from our fields, in comparison of the thousands of bushels which we collect there?" p. 122-126. XIX. EULER'S LETTERS, &c. (Concluded from page 36.) THE HE subjects of the second volume are illustrated in the following order: Letter 1 to 5. On the knowledge of truth; objections of the Pyrrho nists; demonstrative, physical, and moral certainty; with precautions for attaining assurance of sensible and historical truths. —6. Of the knowledge of the essence of bodies. 7, 8, 9. Extension and its divisibility-10 to 17. Of monads, with objections and arguments of monadists, and reflections on the system. -18 to 20. Nature of colours and "The hamster is preyed on by se analogy between colours and sounds. veral animals, but the ferret seems-21 to 39. Of electricity, nature ordained to be its most inveterate enemy. It is not so strong as the hamster, but it is much more active and cunning; and by these means it prevails over him. In summer and autumn, he is the ferret's food. He pursues him, even into his den, and kills him there; and having thus gain ed the victory, he makes it his own habitation. From this he goes out a hamster-hunting, and having found, he seizes him so strongly, that he drags him away and preys upon him. "Even this circumstance shews the wisdom of the Divine Providence. This animal is in hostility with all others, and yet the species is preserved! Every creature is an object of the care of Divine Providence, be cause necessary to the perfection of the whole. The hamster may be objected to because destructive; but were there not such creatures, God would not cause the earth to bring forth so plentifully. For these he makes a provision in our fields, and they can consume no more than he has provided for them. At times they may become a scourge, but when we balance our gains with our losses, we shall find, on the most scrupulous reckoning, that we have sus and explanation of thunder and lightning, with the possibility of preventing and averting effects of thunder. 40, 41. Problem of the longitude, with general description and magnitude of the earth.-42 to 45. Of latitude.-46 to 53. Knowledge of the longitude, by calculation of space passed through, time-piece, eclipses of Jupiter's satellites, eclipses and motion of the moon.-54 to 60. On the mariner's compass and properties of the magnetic needles.-61 to 71. On magnetism.-72 to 108. Of dioptrics, with nature, properties, use, effects, and construction of different kinds of glasses.-109 to 112. Representation and apparent magnitude of sun, moon and stars.--113. The heavens appear under the form of an arch, flattened toward the zenith.114. Reasons for the faintness of the light of heavenly bodies in the horizon.-115. Illusion respecting the distance of objects and the dimi nution of lustre. 116. On the azure colour of the heavens.-117. What the appearance would be if the air were perfectly transparent. 118. Refraction of rays of light in the atmosphere, and its effects, twilight, rising and setting of the heavenly bodies.-119. The stars appear at a greater distance than they are. Table of refraction. Mr. Euler closes his illustrations of electricity with a description of the nature of thunder, and its resemblance to electricity; the latter is evidenced by the following proofs: "Let a bar of metal, say of iron, be placed on a pillar of glass, or any other substance whose pores are close, that when the bar acquires electricity it may not escape or communicate itself to the body which supports the bar; as soon as a thunder-storm arises, and the clouds which contain the thunder come directly over the bar, you perceive in it a very strong electricity, generally far surpassing that which art produces; if you apply the hand to it, or any other body with open pores, you see bursting from it, not only a spark, but a very bright flash, with a noise similar to thunder; the man, who applies his hand to it, receives a shock so violent that he is stunned. This surpasses curiosity, and there is good reason why we should be on our guard, and not approach the bar during a storm. A professor at Petersburgh, named Richmann, has furnished a melancholy example. Having perceived a resemblance so striking between the phenomena of thunder and those of electricity, this unfortunate naturalist, the more clearly to ascertain it by experiment, raised a bar of iron on the roof of his house, cased below in a tube of glass, and supported by a mass of pitch. To the bar he attached a wire, which he conducted into his chamber, that as soon as the bar should become electric, the electricity might have a free communication with the wire, and so enable him to prove the effects in his apartment. And it may be proper to inform you, that this wire was conducted in such a manner as no where to be in contact but with bodies whose pores are close, such as glass, pitch, or silk, to prevent the escape of electricity. 66 Having made this arrangement, he expected a thunder-storm, which, unhappily for him, soon came. The thunder was heard at a distance; Mr. Richmann was all attention to his wire, to see if he could perceive any mark of electricity. As the storm approached, he judged it prudent to employ some precaution, and not keep too near the wire; but happening carelesly to advance his chest a little, he received a terrible stroke, accompanied with a loud clap, which stretched him lifeless on the floor. "About the same time, the late Dr. Lieberkuhn and Dr. Ludolf were about making similar experiments in this city, and in that view had fixed bars of iron on their houses; but being informed of the disaster which had befallen Mr. Richmann, they had the bars of iron immediately removed, and, in my opinion, they acted wisely. "From this you will readily judge, that the air or atmosphere must become very electric during a thunderstorm, or that the ether contained in it must then be carried to a very high degree of compression. This ether, with which the air is surcharged, will pass into the bar, because of its open pores, and it will become electric, as it would have been in the common method, but in a much higher degree." Mr. E. concludes his explanation of the phenomena of thunder and lightning with these observations in Letter 38, and then proceeds to state the possibility of preventing and of averting the effects of thunder in Letter 39. "Thunder then is nothing else but the effect of the electricity with which the clouds are endowed; and as an electrified body, applied to another in its natural state, emits a spark with some noise, and discharges into it the superfluous ether, with prodigious impetuosity; the same thing takes place in a cloud that is electric, or surcharged with ether, but with a force incomparably greater, because of the terrible mass that is electrified, and in which, according to every appearance, the ether is reduced to a much higher degree of compression than we are capable of carrying it by our machinery. When, therefore, such a cloud approaches bodies, prepared for the admission of its ether, this discharge must be made with incredible violence: instead of a simple spark, the air will be penetrated with a prodi gious flash, which, exciting a commotion in the ether contained in the whole adjoining region of the atmosphere, produces a most brilliant light; and in this lightning consists. "The air is, at the same time, put into a very violent motion of vibra tion, from which results the noise of thunder. This noise must, no doubt, be excited at the same instant with the lightning; but you know that sound always requires a certain quantity of time, in order to its transmission to any distance, and that its progress is only at the rate of about a thousand feet in a second; whereas light travels with a velocity inconceivably greater. Hence we always bear the thunder later than we see the lightning: and from the number of seconds intervening between the flash and the report, we are enabled to determine the distance of the place where it is generated, allowing a thousand feet to a second, "The body itself, into which the electricity of the cloud is discharged, receives from it a most dreadful stroke; sometimes it is shivered to pieces; sometimes set on fire and consumed, if combustible; sometimes melted, if it be of metal; and, in such cases, we say it is thunderstruck; the effects of which, however surprising and extraordinary they may appear, are in perfect consistency with the well-known phænomena of electricity. "A sword, it is known, has sometimes been by thunder melted in the scabbard, while the last sustained no injury; this is to be accounted for, from the openness of the pores of the metal, which the ether very easily penetrates, and exercises over it all its powers, whereas the substance of the scabbard is more closely allied to the nature of bodies with close pores, which permit not to the ether so free a transmission. "It has likewise been found, that of several persons, on whom the thunder has fallen, some only have been struck by it; and that those who were in the middle suffered no injury. The cause of this phænomenon likewise is manifest. In a group exposed to a thunder-storm, they are in the greatest danger who stand in the nearest vicinity to the air that is surcharged with ether; as soon as the ether is discharged upon one, all the adjoining air is brought back to its natural state, and consequently those who were nearest to the unfortunate victim feel no effect, while others, at a greater distance, where the air is still sufficiently surcharged with ether, are struck with the same thunder-clap. VOL. I. "In a word, all the strange circumstances, so frequently related, of the effects of thunder, contain nothing which may not be easily reconciled with the nature of electricity. "Some philosophers have maintained, that thunder did not come from the clouds, but from the earth, or bodies. However extravagant this sentiment may appear, it is not so absurd, as it is difficult to distinguish, in the phænomena of electricity, whether the spark issues from the body which is electrified, or from that which is not so, as it equally fills the space between the two bodies; and if the electricity is negative, the ether and the spark are in effect emitted from the natural or non-electrified body. But we are sufficiently assured that, in thunder, the clouds have a positive electricity, and that the lightning is emitted from the clouds. "You will be justifiable, however, in asking, if by every stroke of thunder some terrestrial body is affected? We see, in fact, that it very rarely strikes buildings, or the human body; but we know, at the same time, that trees are frequently affected by it, and that many thunder-strokes are discharged into the earth and into the water. I believe, however, it might be maintained, that a great many do not descend so low, and that the electricity of the clouds is very frequently discharged into the air or atmosphere. "The small opening of the pores of the air no longer opposes any obstruction to it, when vapours or rain have rendered it sufficiently humid; for then, we know, the pores open. "It may very possibly happen, in this case, that the superfluous ether of the clouds should be discharged simply into the air; and when this takes place, the strokes are neither so violent, nor accompanied with so great a noise, as when the thunder bursts on the earth, when a much greater extent of atmosphere is put in agitation." question, and under what obligation I should lay a number of worthy people, were I able to indicate an infallible method of finding protection against thunder. "The knowledge of the nature and effects of electricity, permits me not to doubt that the thing is possible. I corresponded some time ago with a Moravian priest, named Procopius Divisch, who assured me that he had averted, during a whole summer, every thunder-storm which threatened his own habitation and the neighbourhood, by means of a machine constructed on the principles of electricity. Several persons, since arrived from that country, have assured me that the fact is undoubted, and confirmed by irresistible proof. "But there are many respectable characters, who, on the supposition that the thing is practicable, would have their scruples respecting the law. fulness of employing such a preservative. The ancient pagans, no doubt, would have considered him as impious, who should have presumed to interfere with Jupiter, in the direction of his thunder. Christians, who are assured that thunder is the work of God, and that Divine Providence frequently employs it to punish the wickedness of men, might with equal reason alledge, that it was impiety to attempt to oppose the course of sovereign justice. "Without involving myself in this delicate discussion, I remark that conflagrations, deluges, and many other general calamities, are likewise the means employed by Providence to punish the sins of men; but no one, surely, ever will pretend, that it is unlawful to prevent, or resist, the progress of a fire or an inundation. Hence I infer, that it is perfectly lawful to use the means of prevention against the effects of thunder, if they are attainable. "It would, no doubt, be a matter of still greater importance, to have it in our, power to divest the clouds of their electric force, without being under the necessity of exposing any one place to the ravages of thunder; we should, in that case, altogether prevent these dreadful effects, which terrify so great a part of mankind. "This appears by no means impossible; and the Moravian priest, whom I mentioned above, unquestionably effected it; for I have been assured, that his machinery sensibly attracted the clouds, and constrained them to descend quietly in a distillation, without any but a very distant thunder-clap. "The experiment of a bar of iron, in a very elevated situation, which becomes electric on the approach of a thunder-storm, may lead us to the construction of a similar machine, as it is certain, that in proportion as the bar discharges its electricity, the clouds must lose precisely the same quantity; but it must be contrived in such a manner, that the bars may immediately discharge the ether which they have attracted. It would be necessary, for this purpose, to procure for them a free communication with a pool, or with the bowels of the earth, which, by means of their open pores, may easily receive a much greater quantity of ether, and disperse it over the whole immense extent of the earth, so that the compression of the ether may not become sensible in any particular spot. This communication is very easy by means of chains of iron, or any other metal, which will, with great rapidity, carry off the ether with which the bars. are surcharged. "I would advise the fixing of strong bars of iron, in very elevated situations, and several of them together, their higher extremity to terminate in a point, as this figure is very much "The melancholy accident which adapted to the attraction of electricibefel Mr. Richmann at Petersburg, ty. I would, afterwards, attach long demonstrates, that the thunder-stroke chains of iron to these bars, which which this gentleman unhappily at- would conduct under ground into a tracted to himself, would undoubted- pool, lake, or river, there to discharge ly have fallen some where else, and the electricity; and I have no doubt, that such place thereby escaped; it that after making repeated essays, can therefore no longer remain a ques- the means may be certainly discovertion whether it be possible to conducted of rendering such machinery more thunder to one place in preference to commodious, and more certain in its another; and this seems to bring us effect. near our mark. "It is abundantly evident, that on the approach of a thunder-storm, the ether, with which the clouds are surcharged, would be transmitted in great abundance into these bars, which would thereby become very electric, unless the chains furnished to the ether a free passage, to spend itself in the water, and in the bowels of the earth. "The ether of the clouds would continue, therefore, to enter quietly into the bars, and would, by its agitation, produce a light, which might be visible on the pointed extremities. "Such light is, accordingly, often observed, during a storm, on the summit of spires, an infallible proof that the ether of the cloud is there quietly discharging itself; and every one considers this as a very good sign, of the harmless absorption of many thunder-strokes. "Lights are likewise frequently observed at sea, on the tops of the masts of ships, known to sailors by the name of Castor and Pollux; and when such signs are visible, they consider themselves as safe from the stroke of thunder. "Most philosophers have ranked these phænomena among vulgar superstitions; but we are now fully assured, that such sentiments are not without foundation; indeed they are infinitely better founded than many of our philosophic reveries." p. 140 -147. With shouts that might arouse the dead." Then forth Britannia's thunder pours; Return; return, your task is done : Did ever fiercer warfare rage, Let every patriot bosom glow, Beauty, resume thy wonted smile, And, Poverty, thy cheerful brow." Boast, Britain, of thy glorious guests; Peace, wealth, and commerce, all thine own: Still on contented labour rests |