wind a coil so as to take up just enough capacity to be in resonance with the circuit, in so far as the iron core will permit. I only have to add, that I sincerely thank Dr. Pupin, (which Erobably is the wish of all), and that I have profited very much y his lecture, which is a clear and precise exposition of the principle, as well as a most interesting experimental demonstration of electrical resonance with a dynamo machine. [Adjourned.] [communicated After Adjournment By Dr. Pupin.] Mr. Tesla is very kind and generous with his compliments. I do not think, however, that his statement of facts is free from ambiguity. He states that the phenomena of resonance which I have discussed were familiar to him for a long time. My discussion referred to low frequency resonance, whereas Mr. Tesla has, I think, always worked with high frequeucy apparatus, so that his familiarity with low frequency resonance, the subject which I discuss, is probably not based upon his own experimental investigations. At the time when the Perranti effect called forth so much valuable discussion in England, Mr. Tesla1 contributed some remarks to this discussion, which remarks culminated in the following:—"The writer looked for a case of resonance* but he was unable to augment the effect by varying the capacity very carefully and gradually, or by changing the speed of the machine. A case of pure resonance he was unable to obtain. When a condenser was connected to the terminals of the machine * * * the capacity which gave the highest R. M. P. corresponded most nearly to that which just counteracted the self induction with the existing frequency." Mr. Tesla 6tates also in this article that the highest value of the augmentation of the potential which he was able to obtain by connecting a condenser in series to the armature of his high frequency (10' periods per second) machine was only four or five times the impressed E. M. F. What then could Mr. Tesla infer from this result in regard to resonance effects with low frequency? Certainly nothing that was encouraging. At no other time did Mr. Tesla, so far as I am aware, approach the subject of resonance any closer than in the article just referred to. Perhaps Mr. Tesla means that he was acquainted with the phenomena of low frequency resonance which I discussed from the investigations of other men, like Fleming, Kapp, Glazebrook, Swinburne, Lodge, Blakesley, etc.s I appreciate fully the value of the labors of these men, but still I fail to see a very close re 1. Electrical W&rld, N. Y., Feb. 21st, 1891. 2. The meaning of this term Mr. Tesla did not explain. 8. 8ee London Electrician for 1889, 1690 and 1891, also " Fleming's Alternate Current Transformer," vol. ii., p. 401. lation between their work and mine, excepting in one point, and that iB, that they as well as I, have shown theoretically that it is possible to produce a high rise of potential by a combination of self-induction and capacity. I have shown it experimentally also. But I think that I have pointed out very clearly in the course of my lecture that I did not regard the resonant rise of potential as an end but simply as a means to an end, the end being harmonic analysis of E. M. F's, behavior of iron and dielectrics under the inductive action of resonant currents of low frequency, weeding ont of harmonics by means of resonance, etc. With these phenomena Mr. Tesla does not appear to be familiar, either from his own experimental investigations or from investigations of others, excepting those phenomena which Dr. Duncan had investigated some time before me and which I mentioned in the course of my lecture. Report Of The Committee On The Provisional Programme For The Congress. (The following is the appendix referred to in the report of the Committee on the Provisional Programme for the Congress. See page pp. 14 and 2ti ante.) APPENDIX IV. The following is an abstract of a paper read by Mr. E. Hospitalier at the International Congress in Frankfort, 1891, giving the system which the Committee of the American Institute Of Electrical Engineers suggested using as a basis for an International system to be adopted at the next Congress. The object of tint system is to introduce a uniform international system of symbols, abbreviations, etc., for terms used in the electrical science, which shall be as universally adopted and understood as the various signs used in algebra and trigonometry, for instance. In such a system, he states, that it is indispensable to establish a clear and precise distinction between a physical quantity, its magnitude or value, and the unit for measuring such a quantity. A physical formula shows the relation between physical quantities each of which is represented by a special symbol. The magnitude or value of physical quantities are represented by the ratios of the physical quantity and one of the same nature taken as a unit; the magnitudes or values of physical quantities are therefore simply abstract numbers. A unit is a physical quantity of a speciaf magnitude which serves as a measure of quantities of the same nature; these units are designated by special names, and may be represented by abbreviations for the sake of simplification. Symbols representing physical quantities enter into physical formula?, but units never do. In the c. o. s. system, for instance, the three basic physical quantities are length, mass and time, which are represented by the respective symbols L, Mand T; the corresponding units are the centimetre, the mass of one gram, and the second; their abbreviations are cm, g, and s. For derived quantities, definitions are established by equations which show the relation between the fundamental quantities. The physical quantity, surface, for instance would be represented by the symbol S and denned by the equation S = L X L = D and the unit for measuring it is the square centimetre represented by the expression cm. the physical quantity, velocity, represented by v is the quotient of the length by a time and is defined by the equation v = L -~ T — L T~l and the unit is a centimetre per second. This would establish the important and essential distinction between the symbols representing physical quantities, and the units for measuring their magnitude. He suggests using italics, Greek and script letters exclusively for symbols, while for the units and their abbreviations he suggests using Roman letters. He suggests furthermore using the same letters for physical quantities of the same nature whose dimensions are different, or for different physical quantities whose dimensions are the same; he proposes, for instance, to use the symbol W for the physical quantity " euergy," be it mechanical, thermic, chemical affinity or electric; also, to represent the moment of a force or of a couple, as it is, like work, the product of a force and a length. A length and a coefficient of self-induction have the same dimensions and are to he represented by the same symbol L to which in certain cases an index may be added to avoid confusion. He furthermore suggests adopting the system already in use of representing kilometres by km, millimetres by mm, milligrams by mg, etc. Of the six different ways of representing quotients: ... j centimetre cm _, centimetre per second; -—; — ; cm : s ; cm.s , cm/s; second s he recommends using cm : s as the simplest. His suggestions for a complete system of such units and quantities as are used by electricians, is given in the following table which he claims to have modified to conform with the decisions adopted by the Congress of 1891, which have been given in Appendix I. [See next In addition he also suggests the advisability of a uniform system of reference to articles in technical periodicals; this should state the volume, the page, the date and in every case the year. He also recommends that in adopting new names, very great care should be taken: the word " drehstrom " for instance, (which literally means a rotary current) does not correspond to any physical reality; the proper expression would be " polyphase alternating currents." [The undersigned calls attention to the fact that the symbols do not all conform strictly to the adoptions of the Congress of 1891. which decided that Greek letters should be used only for physical constants and angles; Mr. Ilospitalier furthermore uses "small caps for the symbols representing the units, in place of large capitals, a modification which is to be commended, as it avoids confusing A (ampere) with A (acceleration). The chief objection which English speaking people will have to this system is, the changing of the TS K classical expression for Ohm's law from C— — to I — —, and writing /* R for R H C* R. This might be overcome by writing O for current, K for capacity, and / for moment of inertia.] Cart. Hebing, Chairman. |