A cyclopaedia of physical sciences : comprising acoustics, astronomy, dynamics, electricity, heat, hydrodynamics, magnetism, philosophy of mathematics, meteorology, optics, pneumatics, statics &c. &c / by J.P. Nichol with the assistance of eminent scientific men.

  • John Pringle Nichol
Date:
1860
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Licence: Public Domain Mark

Credit: A cyclopaedia of physical sciences : comprising acoustics, astronomy, dynamics, electricity, heat, hydrodynamics, magnetism, philosophy of mathematics, meteorology, optics, pneumatics, statics &c. &c / by J.P. Nichol with the assistance of eminent scientific men. Source: Wellcome Collection.

    937/952 page 903
    11 asain requested the Editor of tlie PhUosnpMcnl . Magazine to say so, and to withdraw every cip- )peai-ance of claim on my part. 'J'his lie did in I the number for June. Again previous to tiie late i dispttte on the subject, finding my name referred : to, in several of the newspapers, as the inventor (of the instrument, I immediately wrote a dis- (claimer to the Courant, and two days thereafter, I more explicitly to the Scotsman. I did consider tthen, however, that I had the priority, although I unimportant, in regard to the particular form of tthe instrument, which has been designated as the ''Ocular Stereoscope;' but, subsequently, when 1 Professor Wheatstone brought forward some (ur- tther information, showing the very early date of this first notice of the subject, and that in b(jth I forms, I wrote to the Times, making a still more sweeping concession as to Wheatstone's priority iin everything; but expressly denying that, either iin the first conception or in the subsequent con- istraction of my instrument, I had borrowed a f single idea from him. If, after my own inven- ttion, I heard of Wheatstone's instrument, it had jso entirely escaped my memory, that in 1852 I rread his description of it with the firm persuasion tthat it was newly brought out. I was led to the i idea of my instrument solely from having been f often for years reverting to a question on which II had formerly written an essay—' On the means I by which the eye conveys the knowledge of dis- itance to the mind.' I thought, if such are the rmeans, the eye might be deceived b}' presenting to i it fictitious data. I well recollect when the deter- rmination first crossed my mind to construct an i instrument for the purpose. It was in walking aalong a footpath through a corn-field in Kent. I idon't know the dale; but as I left Kent in 18.34, :it could not be later; and I gave thnt date to Sir I David, not as the actual date, but as (he. postenur ■limit. I probably mentioned my intent ion to one Or two individuals at the time; but of this I amun- 'certain. More serious business pushed the purpose laside, and I never resumed it till some time pro- libably in 1838 (I gave 1839 again as thewUeiior iilimit from precise data), when my friend. Mr. .'Adie, asked me to contrihutc a paper to the Poly- I'technic Institution. I proposed that subject, and iiimmediately constructed the instrument; but i it gave him no satisfaction, and I laid it aside :ifor the time, intending to bring it out again and Mo improve it. But I always regarded it as a thing : that only a very few would take any interest in ; land such would have been tiie case with all forms ■of the stereoscope, had not photography come to ;!it8 relief, and given it new life. In renomicing iall claim to the invention, in consequence of 'Wheatstone's priority, I may, however, make one exception. The first ap|)lication of the sle- ireoscope to landscapes, or to anything beyond ,-geometrical figures, was certainb) mine; and, indeed, I don't know that I ever thought of ap- I'plying it to anything el-^e than landscapes. Had lithe Times chosen to publish my letter, it would probably have ended the controversy; but ( nnn sic p/ncuit deis), it pleased the said I'imes rather to let the great men fight it out. TIici-nio-IEIcciricity, table referred to p. 837: ELECTRICAL CONVECTION OF HEAT. Ill Ciidminm ..'Positive. Brnss ... ..Positive. Copper ....Positive. Order doubtful. runpi J Lew iTin '] ^1*' Positive. Order doutbful, rlion J Plalin CNiclie 003 Zinc Positive, zero, or negative. Gold Positive, zero, or negative. Silver Pdsitive, zero, or negative. Iron Kegitive. inum Nettative. el Probably negative. Probably f Palladium.. Probably negative, nearly equal. ^Mercury ...Negative. Unirei-sal Instriinient. The notice of this instrument, intended for the text, has been acci- dentally omitted. It is virtually an altitude and azimuth in-itrument of gre:it power, but whose solid dimensions are such that it is quite port- able. The special characterisi ic of it is this:— The telescope, instead of being a straight tube, as is usual in tliis country in all such instru- ments, is broken into two arms at right angles to each other. The break is in the middle of the length of tiie tube; ar.d at the break a solely reflecting prism is placed, which turns the ra}'3 entering the object-glass in a rectangular direc- tion. Tlie eye-piec is, in this way, placed at the centre of the altitude circle; and the telescope becomes free to move through all altitudes. This instrument is much and very deservedly prized on the continent, although coinpariitivelv little known in Great Britain. For instance, Struve has em[)loyed it in all his lar^e surveys. Its theory is not difficult, and its adjustments simple. A full account and discussion of it will be found in Siruve's description of the great observatory at Poulkova, and indeed in every great foreign treatise on Practical Astronomy. Very fine in- struments of this descrifition are made by Ertel of Munich, and Repshold of Hamburgh. A few of them are in this country. Tciitilntioii.—At the close of Hicating op Boii.DiNGs, page 431, ref-rence is made to a sequel to it, which we had assigned to the head- ing VioNTii.ATioN. An admirable practical essay on this most interesting subject has just reached us from Mr. R Ritchie, Civil Engineer, Assoc. Inst. C.E.L. (the author of article on Mhating), which we should most gladly liave printed in addition to the general notice in the text, had space and the press of time permitted. It con- tains so full and scientific an analysis and cri- ticism of all that has been done and proposed on this most essential subject, that we cannot pass the opportunity of expressing the hope that Mr. Hitchij will extend it, and publish it as a sub- stantive work. Mr. Ritchie has already obtained many distinctions from learned societies on ac- count of Ilia labours in this very important field.
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