traction in a limited sphere may still exist as a property arranging the disposition of the atoms, that the Newtonian even of this school is not exempt from giving an attentive consideration to a theory of physics, merely because attraction lies at its foundation.

Though the preceding postulates embrace all the fundamental principles on which Mr. Exley's theory is built, it cannot be denied, that in order to make them apply to an explanation of pheno mena in detail, various subsidiary hypotheses are introduced, for which no reason can be assigned but their convenience, and no proof but their fitness to make facts and theory accord. The impression which this produces on our minds, is that of the extreme ingenuity and elaborate artificiality of the system, and which makes us suspicious whether it be consonant to nature, and imparts to it the character of being a “worldmaking" scheme. It is matter of discussion, whether even the opposite practice of gratuitously multiplying first principles, by continually assigning forces and properties to matter merely to serve an im mediate purpose, and explain only particular facts, or merely with a view to a partial scope and bearing, is more objectionable, or really more productive of complexity, than devising a general and comprehensive theory, whose pre-requisites are so few and simple, as to require complemental and particular suppositions for particular classes of facts, and in many instances for particular cases. Mr. Exley says, that some difficulty must be allowed to have occurred in bringing so few and such simple principles to bear in the explanations," and that "it is not complexity but simplicity which characterises the operations of nature, in all their multiplicity, diversity, and grandeur." I would submit, for Mr. Exley's reflection, that the simplicity which characterises the operations of nature, does not necessarily arise from the fewness, whatever it may from the simplicity, of the first principles; for paucity is not to be identified and confounded with simplicity, any more than multiplicity is with complexity. It often happens that, by laying the foundation of things a little broader, we avoid the necessity of a complicated system of advenient aids, and that by the admission of an additional principle, we are disen

cumbered of a variety of subordinate contrivances, which, in a plan on a narrower basis, are obsolutely necessary, in order to make it work. This is more obvious to the man of practical views than to the theorist, and may admit of many illustrations. Simplicity in operation is not more attributable to simplieity in first principles, than to a due variety of special original qualities, bestowed with a reference to given purposes, inasmuch as direct procedures are less cir cuitous than those which are indirect. The proper medium, the right combination of variety with simplicity of fundamental principles, in order to obtain the greatest simplicity in the operation and working of things, is the cardinal point of wisdom-to this point nature always attains, and it is our part to learn from her, and in our own doings to approximate thereto. "Her causes are few, her effects innumerable, Her course is the easiest and shortest possible, and her means the fewest that can possibly bring about her ends"-consistently, it should have been added, with that same easiest and shortest possible course, or, in other words, consistently with the greatest possible harmony and simplicity in the working out of results. But man will not learn of nature, he prefers rather to roam" in the region of pure intellect,”* and will twist and torture known but inapplicable principles to his purposes, sooner than wait the slow openings of experimental research, and by a patient, laborious, and extensive induction, discover the unknown principles which are really involved in his subject. The history of science has ever exhibited instances of this spirit, and never more strikingly, perhaps, than at the present day, when the physiologists profess to solve the phenomena of life, nay, even the phenomena of mind, on physical principles, and can allow themselves to talk of thought being a secretion of the brain, similar to a secretion of bile by the liver. Where is the philosophy, or rather, where is the common sense of supposing that the simplicity of the ope rations of nature is consulted, by eliciting them from so few principles as suppositions like these would indicate. It ought to be distinctly kept in mind, and

*My acknowledgments are due to Mr. Frend for this expression.

more so than the current phraseology of our language well permits, that to discard multiplicity is not to secure simplicity, which is not its opposite. To resolve all action, whether mechanical, animal, or mental, into one attribute of matter-communicable impulsive motion or to make all the widely different elements to merge into one primeval form -or to sacrifice all the essential distinctions of animal existence, to a vague generalisation of the living principle, and evolve it in all its varied forms from a single original filament, or hypotheses, certainly, which are as obvious for simplicity, if paucity of first principles be only what is meant, as they are for being devoid of all appearance of truth and reality. Such simplicity has a charm for the mere mathematician and the theorist, because it brings a subject apparently, within the scope of his intellect, and gratifies his taste for orderly collocation and consecutive deduction, though the conclusions at which he arrives can possess only a seeming certainty, because the whole of that from which they flow is artificial and delusive. "Such a system," says Professor Sedgwick, for I must again quote this very appropriate passage, which refers to a subject that has often been treated in this eliminating method of obtaining simplicity,-"such a system may delight by its clearness, and flatter our pride because it appears to bring it within our narrow grasp; but it is clear only because it is shallow, while a better system may seem darker only because it is more profound." Let me not, however, be understood as intimating that Mr. Exley has indulged in any such wild conceits as those above enumerated -he has a better conception of what belongs to true philosophy. Still, the mathematical predilection for grounding his theory on very few and simple postulates, has, it is conceived, driven him to the necessity of feigning certain conditions, ere he can frame an explanation in accordance with his principles. Thus, with regard to the magnetical phenomena, there are many things assumed which it is difficult to admit or conceive. To the puzzling inquiry why, of all the metals, iron, nickel, and cobalt, are capable in any particular degree of becom ing magnetical, we must be satisfied with this supposition for an answer, that the ethereal matter" must be capable of en

tering their surfaces to a very small distance, and by pressing and crowding the atoms of the body in its course together, must be incapable of making its way in a straight line, and this condition appears to belong to few bodies." The spiral channelling of magnetic bodies, by a current of ethereal matter gyrating about our globe in spiral lines, together with the local currents in these bodies, and the manner in which they produce attraction and repulsion, are all very difficult to conceive. These suppositions, however, are not more improbable than others that are current, particularly Amperes'; and they have the further advantage of being connected with a very general hypothesis. It is also worth notice, that they are countenanced to a certain extent by the spark which has been obtained from the magnet alone, since Mr. Exley's theory was published. The reader will do Mr. Exley great injustice if he should allow himself to receive an unfavourable impression of his most ingenious and elaborate work, from the above quotation, or, indeed, from any of the slight notices of it which this article contains. It will, doubtless, be referred to many years hence, as containing happy anticipations, in many particulars, of what will then be directly established by experiment. There is some reason to suppose that Newton himself was busily employed at one time in applying the property of attraction to an explanation of the intimate constitution of bodies, as he before had done to an explanation of the constitution of the solar system. Mr. Exley has now made the attempt, with what success time only can develope.

Mr. Exley has invited " any gentleman to point out a single fact, in any department of natural philosophy, which is not in accordance with the theory." I wish therefore to submit a few cases for his consideration. I cannot find that he has explained the expansion of water just previous to its temperature falling to the freezing point, but only in the act of crystallisation. He does not explain the welding of two pieces of iron together. This fact appears rather inconsistent with the theory, for he observes, that "when bodies are dry and warm, their surfaces retain much ethereal matter, parti cularly caloric, which prevents their junction ;" and again, that "soon as the contact [of glass] is broken, the

ethereal atoms are diffused over the surface, and this prevents the union." It will hardly be said that the surfaces of iron in the act of welding are necessarily in a fluid state. In explanation of the explosion which follows the breaking off the tail of what are called Prince Rupert's drops, he does not advert to what I understand to be the fact, that this effect is produced only when the drops are made of the black-bottle glass, and which, if true, will make the matter much more difficult than it is already found to be. Let one of these drops be exploded in water, especially boiled water, and the side of the containing cup or glass will be forced out in a very remarkable manner. How is this effect produced ?-has the liberated ethereal matter sufficient momentum ?-or does it arise from the percussicu produced by the fragments of the glass drop? Can Mr. Exley explain why the magneticneedle is insensible to nickel at a certain very moderate temperature, and notwithstanding glass intervenes to protect it from any current of air produced by that temperature?-and why a plate of hardened steel has a magnetic influence only in fine lines, drawn in any direction on its surface with a pointed magnet? An explanation of this fact is to me inconceivable, according to the manner in which Mr. Exley supposes the communication of magnetism to take place.

There are two incidental topics on which, in conclusion, I wish to offer a few remarks. The first concerns the distinction between theory and hypothesis ; and the second relates to some metaphysical ideas, suggested by Mr. Exley's notion of the constitution of an atom of matter.

(1.) Mr. Exley will perceive by the manner in which I have used the terms theory and hypothesis, that we differ in our opinions of their value. He says, that "the nature of an hypothesis is to explain only the facts which give rise to its contrivance; but a theory extends its influence to other classes of facts not thought of in its construction." prehend that the distinction between these terms, ought not to rest on their application being more or less general, but on a more exact and special difference of kind instead of degree. Thus I would use the term hypothesis, in its extensive signification, in reference to a

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system which is founded on postulates, whether gratuitously assumed, or analogically denied; but the term theory, I would apply to a system whose first principles are ultimate natural facts or truths, whether self-evident, or analytically traced through a course of observation or experiment. This is the broad primitive distinction; but it may be gradually lost as hypothesis merges into theory, by the postulates becoming gradually converted into fundamental truths. This is, I conceive, the proper philosophical use of the terms as applied to co-extensive subjects; but in a limited, and especially in a mathematical, sense, Mr. Ex ley's explanation of the term hypothesis is correct. In the mathematics, indeed, an hypothesis is not merely "to explain only the facts which give rise to its contrivance;" but it is, in general, a palpable invention by the mathematician, not to explain or investigate a series of complicated facts in their natural action and sequence, but to squeeze the subject within the narrow compass of his art and means. Nature is feigned to act in that way and manner in which the mathematician can follow her with rule and measure in his hand, and her actual proceedings are no otherwise regarded than as a guide to enable him to frame the imagined process, so as to produce similar effects. It is needless to say, it is only by chance, or by an especial after-contrivance, that the result can be the same; and hence, by a misuse or by an unguarded use of terms, it is commonly said that theory and experiment never agree. This consideration leads to a statement of the distinction in another manner. Theory admits not of any thing which is known to be untrue; it is not worthy of the name unless it is conformable to nature as far as it goes. It may, however, be incomplete though not incorrect, and hence arise the frequent discrepancies between its results and those of experience; but when it comes to us perfect as a whole, those results must necessarily accord. How seldom this is the case it is not necessary here to say. Hypothesis, on the other hand, admits of suppositions which are only thought to be true; and, in the mathematical sense, it even admits those which are known to be false. In the latter case it cannot agree with practice; and hence experiments, or obser

vations, on those subjects which admit only of hypothesis, must be the ultimate resort, if we would wish our conclusions to have any value. To this, indeed, we are generally driven, in reference even to theory, because of its incompleteness, or of the impossibility in most cases of comprising all the possible influences that are implicated in the final issue. (To be continued in our next.)

ON THE PRACTICE OF THE BLOW-PIPE.

Dear Sir,-Among the numerous contributions which have at various periods appeared in your pages relative to the construction and management of blowpipes, I have been surprised at not finding any directions for the practice of the mouth blow-pipe; an instrument far exceeding, in utility and convenience, all the artificial combinations which have been invented to supply its place. Thinking, therefore, a communication on the subject likely to prove interesting to your chemical readers, and calculated to promote the employment of this useful little instrument, I am induced to solicit your insertion of the following practical, though somewhat desultory, remarks, and am, Yours, very truly, LIBERTUS.

Newington, March 9, 1835.

the

The introduction of the use of the blowpipe in practical chemistry maybe regarded almost in the same light as the application of the power of steam to the purposes of commerce. If the latter has increased our national resources, and forwarded the interests of mechanical science, by economising the labour and expenditure which were formerly bestowed former has in like manner advanced the cause of chemistry and its dependent sciences, by reducing the expense of fuel, time, and material, which were originally required in qualitative analysis. If the mechanic can now produce, with comparative ease and expenditure, an article which, before the introduction of the steam-engine, would have required the labour of many weary days, and the consumption of much valuable materialthe modern chemist can, with equal facility, detect the constituent principles of a body which, before the invention of the blow-pipe, would have called in requisition the unremitting exertions of many tedious nights, and the profuse employment of many rare and, perhaps,

valuable substances. In fact, by the introduction of this simple, yet invaluable, instrument, the modern chemist can, by his parlour fire-side, and with a common candle, perform those operations, to accomplish which the ancient and less gifted philosopher would have been compelled to resort to the unhealthy atmosphere of a laboratory, and the continued poring over an intensely active fire. The blow-pipe, according to Bergman, had been long employed in the arts by jewellers and others, for the purpose of soldering, before it was applied to the purposes of analytical chemistry and mineralogy, by a Swedish metallurgist of the name of Sual, about the year 1733. This individual appears, however, to have left no written account of the methods which he adopted in its application. The researches of Cronstedt, Bergman, and Gahn,-and, more recently, those of Berzelius and Faraday, have concurred in raising this instrument to the eminent station of utility which it at present enjoys. In the work of Berzelius on this subject, will be found ample instructions for the pursuit of mineralogical and analytical chemistry; and in the "Chemical Manipulations" of Dr. Faraday, the student will meet with copious directions for applying this instrument in the bending and blowing of glass, in practical chemistry. For the former purpose, the mouth blow-pipe possesses undeniable advantages; but for the more fatiguing operations of the latter, the table or hydrostatic blow-pipe will be found convenient. The advantages possessed by the mouth blow-pipe over all those instruments, whose blast is produced by artificial means, consists in its portability, economy, and the facility of immediately suspending or modifying the blast. "The chemist does not possess," says Dr. Faraday, a more ready, powerful, and generally useful instrument than the mouth blow-pipe, and every student should early accustom himself to its effectual use and application."

The supply of a continued stream of air is the chief difficulty which a beginner experiences in learning the use of this instrument; and this difficulty is, I apprehend, not unfrequently increased by the employment of a blow-pipe with too large an orifice, in the first instance. The following method of constructing

be gradually withdrawn, as represented in fig. 4, till it terminates in a point; this point should be held for a minute or two in the point of the flame, in order to thicken it, and when cold, it is to be ground away with a file, until the smallest possible orifice is visible. The pupil will now be possessed of a blowpipe (fig. 3) with an exceedingly minute jet, and if he puff out his cheeks to the utmost, and place the end b within his lips, while the other extremity is held within a short distance of a candle (fig. 5), he will, after a few trials, find no difficulty in keeping the flame continually, and without intermission, horizontal and clear. The operation which he will be required to perform, in order to keep his cheeks constantly distended, notwithstanding the escape from the jet, cannot easily be described, but will naturally offer itself when the expenditure of air is very small. When the pupil has succeeded in keeping up a constant blast for several minutes by this means, he may enlarge the aperture by degrees, practising between each enlargement, till he finds he can manage a blow-pipe with a large bore, when he should purchase one of brass, with an ivory or tinned mouthpiece, for general use.

Among the numerous hydrostatic blowpipes which have already appeared in your Magazine, the pupil who wishes to manufacture his own apparatus, may assuredly find one which will form a substitute for the table blow-pipe.

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cured. A B is a common pail, about half filled with water; c is a large flower-pot inserted, and fastened in by any convenient method; d is a mouth blow-pipe (glass would do on an emergency), fastened in air-tight, with a cork. and lute, to the hole at the bottom of the flower-pot; e is a bent tube of glass or metal, terminating under the mouth of the flower-pot. When air is blown in from the mouth at e, it rises into the body of the internal vessel and displaces the water, which, in endeavouring to regain its level, forces out the air from the jet of the blow-pipe, with a force proportioned to the height of the column of water displaced.