62 +.01980 63 64 66 67 68 69 70 71 +.06249 +.01178 .9356 78 +.09583 +.03323 +.01916 .9048 .9337 79 +.09791 +.03427 +.01973 .9030 +.03643 +.02090 .8992 .8973 .8955 +.11458 +.11666 +.04503 +.02549 .8862 +.11874 +.04633 +.02618 .SS44 +.12083 +.04766 +.02688 +.03020 +.01752 '.9105 To find the specific gravity of any mixture of air and aqueous vapour by means of this table, we must proceed as follows:Note the temperature and the point of condensation by the hygrometer; if they coincide, that is to say, if the air be in a state of saturation, we shall find the specific gravity required in the fifth column opposite to the proper degree of heat in the first column. If the point of condensation be below the temperature, we must look for the amount of the alteration of volume due to the heat in the second column, and for the expansion due to the vapour in the third column. Add these together, if they have like signs; or subtract one from the other if they have different signs. As the volume corrected by this quantity is to the original volume, so is the standard specific gravity to the specific gravity, as affected by the expansion or contraction. To this must be added the increase of weight due to the vapour in the fourth column, and the result will be the correct specific gravity sought. For example-If we wish to know the specific gravity of a mixture of air and vapour of the temperature of 60°, and of which the dew-point is 40°; we find in the second column opposite to 60° the number +.05833, and in the third column opposite to 40° we have +.00934: the sum of which is +.06767 ; therefore 1.06767: 1 :: 1: 93668. In the fourth column opposite to 40° we find +.00580, and .93668.00580.94248; which is the correct specific gravity under the assumed circum stances. ART. XIII. On the Barometer. By J. F. Daniell, F.R.S. THE following paper requires a few words of preface. It contains, as far as I am able to recollect, the substance of a communication which I had the honour to make to the Royal Society, in the month of November last, before the commencement of their last session. As, with a former paper upon the same subject, a mistake had arisen, as I was informed, from my not having expressed a desire to have it read, the consequence of which was that it was not read, I took the precaution of placing the present manuscript in the hands of the President, with a due notification that it was presented for the purpose of being read at the meeting of the Society. I went, immediately afterwards, upon the Continent; where I was detained several months. Upon my return, in June, I found that the first part of the Philosophical Transactions for the year had been published, and that it contained no notice of my paper: neither could I find that any communication had been sent to me of its destination. I was naturally anxious to obtain some intelligence respecting it, and addressed a note upon the subject to the President; to which he returned me the following reply: Dear Sir, 26, Park-street, June 5. Your paper was read to the Royal Society many months ago, and has been before the council. There was but one opinion expressed as to the ingenuity of the method of preventing the introduction of air, supposing the cause that which you have assigned. The existence of this cause for the appearance of elastic matter in barometer tubes, was not considered, however, as proved by the experiments you have detailed, and it was therefore agreed by the council to wait for your return, in hopes that you might be able to give them some new details or elucidations from the researches which you stated were in progress. I am, dear Sir, Very sincerely your's, H. DAVY. I immediately returned the following answer, being anxious to publish the paper in the ensuing Number of this Journal; but not acquiescing sufficiently in the reasons assigned by Sir H. Davy to withdraw the paper from the judgment to which I had submitted it. * It was read, I am informed, on the 20th January, and several papers which were delivered in after its communication were read before it. My dear Sir, I have no new details or elucidations to communicate to the Royal Society. I shall therefore be much obliged to you to have my paper again brought before the council for their final determination; unless indeed I am to understand that their determination has been already expressed. I have the honour to be, dear Sir, To Sir H. Davy, Bart., Very truly your's, J. F. DANIELL. President of the Royal Society, &c. In consequence of this, the paper was again laid before the council, just before the recess; when, on account of a division of opinion, their determination was postponed to next year. A member of the council then asked leave to withdraw the paper, in order to allow of its publication elsewhere, and stated that I had neglected to preserve a copy of the manuscript. The President, I am told, objected to this, and laid down the law, that the paper having been once taken into consideration by the council, could not be withdrawn. To make sure that no formality was neglected, I immediately addressed the following note to the President : My dear Sir, Gower-street, 25th June, 1825. Understanding that the decision upon my paper is postponed to next year, I beg permission to withdraw it. I remain, dear Sir, Your's faithfully, To Sir H. Davy, Bart., J. F. DANIELL. President of the Royal Society, &c. This is a To this application I never received any answer. brief statement of facts, upon which I shall abstain from making any comment. Twice before I have experienced similar treatment from the council of the Royal Society, and twice before I have appealed to the scientific public with success. I shall now endea. vour, from memory and such rough notes as I have preserved, to recompose the paper, with a full conviction that the facts narrated are of sufficient importance to call for immediate publication, and satisfied, by the opinion of those who are well qualified to judge, that there is sufficient proof of their existence to satisfy all impartial minds that the subject is well worthy of that further investigation which it was my purpose to propose to the Royal Society. A new law has now been promulgated by the President of the Society, and every thing henceforward published in the Philoso phical Transactions must be considered as proved. The council will doubtless immediately drop the notice which has always hitherto been published in the preface to the volumes, that "they do not pretend to answer for the certainty of the facts or propriety of the reasonings contained in the several papers published, which must still rest upon the credit or judgment of their respective authors;" and they will, of course, be careful that this law is administered with impartiality. In such a regulation I, as an humble individual, cannot but acquiesce; but, with many others I imagine, I shall always be found to resist the curtailment of the hitherto-acknowledged right of an author to withdraw a paper, any time previous to the decision of the council upon its publication. In the year 1828 I presented to the Royal Society a paper upon the Construction of the Barometer, the substance of which I afterwards published in my volume of Essays, the original paper having been committed to the archives of that learned body. I therein stated my reasons for differing from the high authority of the President, upon the cause of the existence of elastic matter in barometer tubes, suggested by him in a paper upon" the electrical phenomena exhibited in vacuo," and published in the Philosophical Transactions for the year 1822. Sign. Bellani also arrived at the same conclusion as myself, from a series of experiments which he undertook, expressly to determine whether the air or vapour, the last portions of which are found to remain so obstinately in barometers and thermometers, is introduced with the mercury, or is a portion of that which originally occupied the tube before the VOL. XX. G |