Part 25

Several modes of counteracting the pressure of a decreasing column of mercury having been thought of in conjunction with Mr. W. Cox, the following was at last adopted as the most simple and effectual.

Plate 1 Fig. 1, represents a section of the machine, which consists of a strong glass cylinder A cemented to one of the same kind B, fitted to the solid block C, into which the glass tube D is cemented for conveying air into the moveable receiver E.

The brass axis F, Fig. 2, having a double bearing at _a_, _a_, is terminated at one end by the wheel G, the circumference of which is equal to the depth of the receiver, so that it may be drawn to the surface of the mercury by the cord _b_ in one revolution; to the other end is fitted the wheel H, over which the balance cord _c_ runs in an opposite direction in the spiral groove _e_, a front view of the wheel H is shewn at Fig. 3.

Having loaded the receiver with the weight I, something heavier than may be necessary to force it through the mercury, it is balanced by the small weight K, which hangs from that part of the spiral where the radius is equal to that of the wheel G, from this point the radius of the spiral must be increased in such proportion, that in every part of its circuit, the weight K may be an exact counterpoise to the airholder. In this way, so little friction will be produced, that merely plunging the lower orifice of the tube D under mercury contained in the small vessel L, will be sufficient to overcome every resistance, and to force the gas discharged from the beak of a retort into the receiver, where whatever may be its quantity, it will be subjected to a pressure exactly corresponding to that of the atmosphere. The edge of the wheel H being graduated, the balance cord _c_ may be made to indicate its volume.

Should it at any time be necessary to reduce the pressure to the medium standard of the barometer, it may easily be done by graduating the lower end of the tube D, and adding to the weights I or K, as may be found necessary; the surface of the mercury in the tube pointing out the increase or diminution.

The concavity at the top of the internal cylinder is intended to contain any liquid it may be thought proper to expose to the action of the gas.

The upper orifice _f_, with its ground stopper, is particularly useful in conveying air from the retort _g_, with its curved neck, into the receiver, without its passing through the tube D. In all cases where a rapid extrication of gas is expected the retort _g_, should be firmly luted to the orifice and the weight I, removed from the top of the receiver, this by diminishing the pressure, will admit the gas to expand freely in the airholder at the instant of its formation, and prevent an explosion of the vessels. The same caution must be observed whenever any inflammation of gas is produced by the electric spark.

The air may be readily transferred through water or even mercury by the tube _h_, Fig. 1.

To prevent an absorption of mercury in case of a condensation taking place in the retort made use of for generating air, Mr. Davy has applied the stop-cock _i_, to which the neck is firmly luted. This stop-cock is likewise of great service in saturating water with acid or alkaline gases, which may be effected by luting one end of the tube _k_ to the stop-cock, and plunging the other into the fluid in the small vessel _l_, cemented at top, and terminating in the bent funnel _m_—the tube _h_ having been previously removed, and the lower orifice of the tube D either sunk to a considerable depth in mercury, or closed with a ground stopper. The bend of the funnel _m_, may be accurately closed by the introduction of a few lines of mercury.

The application of the stop-cock _n_, has enabled Mr. Davy to perform some experiments on respiration with considerable accuracy.

_Note._ This apparatus was first described in the third part of Dr. Beddoes’s Considerations; its relation to Mr. Davy’s experiments with the improvements it has lately received, may probably be deemed sufficient to excuse the re-printing it.—The weight I. Fig. 2, having been omitted in the plate, the reader must supply the deficiency. W. C.

PROPOSALS FOR THE PRESERVATION OF ACCIDENTAL OBSERVATIONS IN MEDICINE.

In times beyond the reach of history, the medicinal application of substances could have arisen from no other source than accident. Among articles of the materia medica of known origin, we are indebted to accident for some of the most precious.

Accident is every day presenting to different individuals the spectacle of phænomena, arising from uncommon quantities of drugs on the one hand, and on the other, from uncommon conditions of the system, where ordinary powers only have been knowingly or recently applied. What is said of drugs may be extended to natural agents and mental affections.

From conversation with a variety both of medical practitioners and unprofessional observers, the author of this proposal is persuaded that such authentic occurrences only, as have presented themselves to persons now living would, if they could be brought together, compose a body of fact, so instructive to the philosopher, and useful to the physician, that he despairs of finding a term worthy to characterize it.

In some cases, the influence of unsuspected powers would be detected. In others, resources available to the purpose of restoring health in desperate situations would be directly presented, or could be detected by a short and easy process of reasoning. Some anomalous observations, by shewing the absence or agency of contested causes, would perform the office of _experimenta crucis_—Unusual affections occur of which an exact account would be among the means of removing from physic its opprobrious uncertainty: for this uncertainty frequently depends upon our inability to distinguish the subtler differences in cases which resemble each other in their grosser features.

No striking fact can be accurately stated, in conjunction with its antecedent and concomitant circumstances, without improving our acquaintance with human nature. Our acquisitions in this most important branch of knowledge, may be compared to a number of broken series, of which we have not always more than one or two members. But every new accession bids fair to fill up some deficiency; and a large supply would contribute towards connecting series apparently independent, and working up the whole into one grand all-comprehending chain.

There are complaints, and those by far too frequent, where no known process has a claim to the title of _remedial_. Here the whole chance of preservation depends on the physician’s capacity for bringing together facts that have heretofore stood remote. But no power of combination can avail where there are no ideas to combine.

Every new observation therefore, may be considered as a standard trunk, sending forth analogies as so many branches crowned with blossoms, some of which cannot fail to be succeeded by salutary fruits. And were it not absurd to extend the illustration of so plain a point, it might be added, that when by the continual interposition of new trunks, the branches are brought near together, the produce of each will be ennobled by the action of their respective principles of fecundation.

Whenever the author has been able to obtain certain information concerning any unusual appearance in animal nature, it has been his custom to preserve it; and among his papers he has memorandums which prove that to our present circumscribed ideas concerning the dose of medicines may be sometimes imputed failures in practice; that certain signs are not to be taken in the received signification; and that many measures are adopted or omitted to the detriment of invalids, because it is assumed that circumstances are necessarily connected which may exist separately, or that one given natural operation is inconsistent with another, to which it may really be synchronous or next in order.

Assiduous observation of the daily states of the human microcosm will be the unfailing consequence of attention to its striking phænomena. Such is the progress of curiosity. Such the origin of all the sciences. The more uniformly clear the sky under which they tended their flocks, the less likely were the shepherds of Chaldæa, to found the science of the stars. And however the disposition to study astronomy might have been strengthened by the coincidence between the heliacal rising of Sirius and the overflowing of the Nile, it must, I conceive, have been awakened by the aspect of meteors and eclipses.

Whatever minute and authentic information this imperfect statement may produce, as soon as it shall amount to a certain mass, the author will present it to the public arranged. He flatters himself that no correspondent will eke out by supposition the defect of genuine observation, without clearly distinguishing the one from the other. He still more confidently hopes that none will be instigated by this advertisement to exercise his invention in the manner of Psalmanasar and Chatterton. Whether any literary forgery can be innocent is questioned—but a forged medical report is a drawn dagger which the arm of a credulous physician may any day plunge into the heart of his defenceless patient. The author has heard some inconsiderate wits avow, that they have transmitted to the venders of quack medicines imaginary cures, attested by fictitious signatures; and it is not without apprehension from the propensity of men to display ingenuity and to relate wonders that he announces the present design. But he shall be on his guard, and hopes to baffle attempts at imposition.

THOMAS BEDDOES. RODNEY-PLACE, Clifton, June 1800.

END.

ERRATA.

Page 19 line 15 for _is_ read _are_ — 35 — 7 — for _principle_ read _principles_ — 42 — 11 — for _take_ read _takes_ — 68 Table 5 — for 5,88 read 15,88 — 94 — 4 — for 1¹/₁₂ read ¹/₁₂. — 95 — 4 — for 37 read 30,7 — 96 — 3 — for 38 read ¹/₃₈ — 105 — 9 — for _exactitude_ read _exactness_ — 129 — 21 — for 41 read 4,1 — 132 — 4 — for _into_ read _in_ — 143 — 13 — for 25 read ,25 — 186 — 15 — for _by_ read _from_ — 208 last line — for _abstracted_ read _attracted_ — 238 — 5 — for _gas_ read _oxide_ — 259 — 4 — for 12 read 2 — 283 — 4 — for _potash_ read _iron_ — 315 — 14 — dele _in_ — 409 — 15 — for _respiration_ read _expiration_ — 464 — 10 — for _latter end_ read _end_ — 543 — 3 — for _exhalation_ read _inhalation_.

A few literal errors are left to the reader’s correction.

N. B. The term ignited is sometimes used to signify any temperature equal to or above a red heat, whether applied to solids, fluids, or aëriform substances.

The reasons for the use of the terms nitrogene and nitrous oxide, are given in Mr. Nicholson’s Journal for January.

_Speedily will be Published_

OBSERVATIONS on the External and Internal Use of NITROUS ACID.

Demonstrating its PERMANENT EFFICACY in VENEREAL COMPLAINTS;

And extending its use to other dangerous and painful Diseases.

COMMUNICATED By various Practitioners in EUROPE and ASIA.

TO THOMAS BEDDOES, M. D.

_Of the Publisher may be had, price 1s. 6d._

NOTICE of OBSERVATIONS AT THE PNEUMATIC INSTITUTION, _By THOMAS BEDDOES, M. D._

This Notice contains some trials of nitrous oxide by healthy persons, not in the present work, and some cases of palsy successfully treated by that gas.

_Printed by Biggs and Cottle, St. Augustine’s Back._