the circumstance of their specific gravity being such that they remain suspended in the air without any tendency to descend, and even on frequent occasions are seen to ascend; whereas if they consisted of round drops without any internal vacuity, their descent would be rapid. Water is 828 times heavier than air; and it has been calculated that a drop whose diameter is no more thanth of an inch would acquire a descending velocity of nine or ten feet a second. Besides, if clouds consisted of drops without any internal vacuity, every time the beholder looked towards them with his back to the sun, he would see a rainbow; but this is not the case except when rain is falling.

"But then comes the inquiry, how the distension of the vesicles so diminishes their specific gravity as to cause their suspension at an elevation in the atmosphere.

"It is obvious that the aqueous vesicles composing clouds must by some means or other displace an amount of air, the weight of which is exactly equal to their own weight. If they displaced more, their specific gravity would be less than that of the air by which they are surrounded, and they would consequently ascend to a greater altitude; if they displaced less, their specific gravity would be greater than the air by which they were surrounded, and they would accordingly descend to a lower level. Now as the vesicles composing clouds and the aeriform matter which they contain must be expanded and rendered specifically lighter by every increment of temperature, it may be concluded. that their greater mean temperature than that of the air in which they float, is one of the causes of their suspension at an altitude in the atmosphere. And the greater variations of temperature which they undergo than that of the air in which they float, is probably the principal reason why they have a tendency to rise to a greater altitude at one time, and to descend to a lower altitude at another."-Hutchinson's Meteorological Phenomena, pp. 152, 155, 158.

The same views are entertained by Dr. Thomson.

"Clouds differ from fogs in their altitude and suspension, but in composition they are alike, having the ultimate constituents of water for their ingredients. The proximate cause of their formation is the loss of caloric in the humid atmosphere, and condensation of the moisture; but we are still ignorant of the ultimate cause of the phenomenon. Of their mode of suspension, their specific gravity being lighter than that of air, some have received this as a satisfactory explanation, but it is far from being

cogent [unless accompanied by a theory that accounts for that lightness]. Professor Stevelly of Belfast, offers a theory combining the gravitating force of the vesicles-which through their extreme minuteness is exceedingly trifling, for the weight decreases directly as the cube of the radius-with an electrical hypothesis. A far more plausible theory than the first attributes it to currents-upwards and horizontal. Another hypothesis assigns it entirely to electrical agency. We know that electricity has much to do with the phenomenon; it is largely developed during evaporation . . and the vapor acquires that form denominated positive, while the water which remains is negatively charged.

"That clouds are often largely charged with one of the forms of electricity is abundantly manifest. Canton observed this, and found that the electricity would alternately change from positive to negative five or six times in thirty minutes; which Crosse has confirmed. Why certain clouds should be positively, and others negatively charged, is not yet determined, though the fact is incontestable. . In whichever state, then, the electricity exists in the aggregate, there will be a repulsion and attraction of the particles, by virtue of the law, that bodies similarly electrified repel, while those in the opposite electric states attract each other. As the temperature of the vapor decreases, and the humidity becomes condensed, its capacity for electricity lessens and a portion separates. It is easy to conceive that this electricity accumulates around the individual molecules, and prevents the coalescence of the vesicles into drops, the specific gravity of which would cause their precipitation. Thus they are buoyed in the air, till other influences cause their descent.

"Thunder clouds generally float at altitudes of from 3000 to 5000 feet, though they have been seen so high as 15,000. Clouds have been observed over the summit of Chimborazo at an altitude of about 21,500 feet. In proportion to their lightness, they will generally be found suspended higher in the atmosphere; the lightest of all, viz. the cirri occupying the loftiest strata of the cloudy region."-Thomson's Introduction to Meteorology, pp. 123-125.

These writers thus agree in maintaining that the reason that clouds float in the air at their several elevations is that they are relatively lighter than the atmosphere in which they are upborne. The only question on which they differ

respects the causes of that relative levity; whether it is the structure of the vesicles, the temperature of the clouds, electricity, or perhaps all of these united. For the office which the theory of vesicles and electricity fills, is simply to account for the relative lightness which the particles, after they have passed from invisible vapor into mist, still retain above the air in which they are enveloped. The effect of electricity, Dr. Thomson holds, is to prevent the vesicles which are relatively lighter than the air, from coalescing into particles of such size as to be heavier than the air; and with that theory he regards their inferior specific gravity as the true explanation of their suspension at the heights at which they float.

Mr. Blake thus again here, as everywhere else, in place of establishing his charge against us, only shows himself to be disgracefully unacquainted with the subject of which he affects to talk so learnedly. Was ever a more odious spectacle exhibited by an ignorant, insolent, and reckless charlatan? He not only knows nothing himself accurately; he has the unparalleled impudence in the name of science to arraign and denounce the knowledge and assertion of indubitable facts and truths as proofs of extraordinary superfi ciality and ignorance!

The discreditable blunder we have now pointed out forms the cadence of his labored attempt to establish the charge against us of a "misconception and misapplication of the most elementary principles of science." We might follow him through the remainder of his article, in which he treats of other topics, and convict him of similarly disgraceful errors and unpardonable misrepresentations. But we have no further space to bestow on him, and have given sufficient proofs that he has no title whatever to respect either as a chemist, a geologist, or a writer. Not the least reliance is to be placed on his word or his judg ment. He betrays at every step an inacquaintance with facts and principles, and a lack of comprehension, that form a ludicrous contrast to the lofty pretensions he makes to exact knowledge; while the boldness and malevolence. with which he misrepresents and calumniates, bespeak a still more odious defect of the heart. Not the faintest trace of candor appears in his essay, not the slightest disposition

to notice even the most unanswerable objections to his theories; his aim being not to establish truth, but to overthrow it; not to confute arguments, but to disarm them of their power by caricature and abuse.

We cannot but be surprised that the Editor of the Southern Presbyterian Quarterly should have admitted to his pages an article bearing on its face so openly the character of a personal and malevolent attack. He introduces it to his readers by the following note of commendation :

"We cheerfully give place in our journal to this interesting and able article, and would invite the reader's attention to it, although we do not, of course, pretend to be competent judges of the scientific aspects of it, and although, moreover, we cannot say that we are satisfied with its arguments respecting the meaning of certain places of Scripture." But, as the interest and ability of the article, if it have any, depend on the truth and pertinence of its scientific statements and criticisms, on what ground could the writer of this note commend it as "interesting and able"-if not "competent" to judge of it in that relation-if on the only point on which he felt adequate to criticise it, he regarded it as obnoxious to objection? We cannot suppose this gentleman was pleased with it simply because of its injustice and insolence to us. Was he misled by the profession and station of its author? Was that which prompted him to publish it extraneous to the article itself? Did he deem it impossible that such a tissue of bold and vaunting accusations could be the work of mere ignorance, perverseness, and malignity? Whatever may have induced him to insert it, having sufficiently shown its detestable character, we leave it to the scorn and reprobation to which its truthlessness, malevolence, and meanness, must consign it with all honorable minds.

ART. IV. THE GOLDEN IMAGE, Daniel iii.-NEBUCHADNEZZAR'S VISION OF THE TREE, Daniel iv.

THE office of the events narrated in the second chapter was, on the one side, to show the falsehood of the pretexts

of the Babylonian necromancers to a supernatural knowledge of the future or the past; on the other, to manifest the omniscience of Jehovah, and make known to Nebuchadnezzar and the Hebrew captives, and through them to the generations that were to follow, that four great conquering and oppressing monarchies were in succession to rule the nations of the earth, among whom the Israelites were to be scattered, and that the last in the train was at length to be swept to destruction by a kingdom which Jehovah was to establish, that is to embrace the whole earth and continue for ever. The design of the events related in this chapter was, on the one hand, to demonstrate the nothingness of the idol gods whom the Babylonians worshipped, from the noninterposition of the deity represented by the golden image to preserve his worshippers, and destroy those who refused the homage enjoined by the king; and on the other, to exemplify the supremacy of Jehovah the God of the Hebrews, over all, and his readiness to defend his worshippers from the most powerful enemies, and deliver them from the greatest dangers. The spectators of the scene saw that the image Nebuchadnezzar had set up, was but an unconscious shape. It made no movement, nor did the god imagined to be enshrined in it, to protect its votaries who approached the furnace, from destruction by the flames; nor to make the fire effective on the Hebrews that were cast into it. It failed, therefore, to act the part of a god on an occasion, when, if it had been a deity, it would infallibly have displayed its power as such, and verified its title to the imposing homage that was paid to it by the monarch and princes and chief officials of the greatest empire on the earth. Its silence, its motionlessness, its insensibility to the jeopardy of its reputation, and the peril of its worshippers, showed that it was not a god. If it gave no signs of consciousness in such an exigency, it was vain to expect that any event could rouse it into sensibility. In contrast to this, they saw from the miracle Jehovah the God of the Hebrews wrought for the deliverance of his worshippers, that he was present, all-knowing and all-powerful; that he had control of the elements, that he could defeat the mightiest monarch in his purposes, and that he delivered in the most marvellous manner those who put their trust in him. And these