June 2 1, 1877] 



NATURE 



151 



brightness." This ceases to be true when negative logarithnns 

 are involved. The yellow of the spectrum comes very near the 

 colour of brightness. From these considerations a diagram has 

 b^en constructed showing the colorific elTects of mixing white 

 with any part of the spectrum. The results of theory as shown 

 by the diagram, closely accord with those of experiment upon 

 the sensation of colour. 



Prof. Rood also presented a paper on Newton's use of the 

 term "Indigo" as a prismatic colour. It was intended to 

 indicate the range of the spectrum between the blue and the 

 blue-violet regions. The order of refrangibility is thus stated : 

 prussian-blue and indigo ; cobalt blue ; genuine ultramarine 

 blue ; artificial ultramarine blue. 



Prof. Joseph Le Con'e, of California, sent a communication 

 on the structure of the crystalhne lens and its relations to peri- 

 scopism. The discovery of Dr. Hermann, and his deductions 

 therefrom, were first considered. These are that the crystalline 

 lens, by its structure, is endowed with the property of forming 

 distinct images of objects though lying on the extreme margins 

 of the field of view, of forming perfect images on the retinal 

 screen, even to the extreme anterior margin-. Thus the eye has 

 an enormous field of view compared with optical instruments. 

 The purpose of the structure is to give periscopism to the eye. 

 Prof. I.e Conte believes, however, that as far as periscopism is 

 concerned this structure is of little if any value in man for want 

 of a corresponding suitable retinal structure. The indistinct- 

 ness of the retinal image is different from the indistinctness of 

 an imperfect perception of the image, the former being due to 

 the properties of the lens, the latter to the organisation of the 

 retina. In proportion as we go upward in the scale of animal 

 li/e we find the powers of the central spot of the optical appa- 

 ratus more thoroughly developed for the purposes of binocular 

 vision. 



Prof. A. Mayer, of Stevens Institute, presented four com- 

 munications. He described a "Vernier microscope," which he 

 believes to be new. The object is to substitute an accurate and 

 permanent scale cut on glass for the varying errors of a micro- 

 meter screw. The instrument is of small cost and its errors are 

 not varying. On a glass plate a series of lines is cut in tenths of 

 millimetres ; the central millimetre is divided into ten parts. 

 This scale slides in carefully wrought guides in front of the 

 objec'.ive of a firmly fixed microscope. In the focus is another 

 scale so adjusted that ten of its paits accurately subtend the 

 image of i^ijths of the millimetre scale. Thus a Vernier is 

 formed which rtads down to the tuVu''i of ^ mdlimetre. The 

 glass slide is so shaped that its rounded conical end abuts 

 against the object to be measurrd. Readings to the iuU capa- 

 city of ihe instrument can be quickly obtained. 



Prof. Mayer descrii ed his apparatus for measuring the ex- 

 pansion of metals and alloys under differences ol temperature. 

 It is believed that the coefficients of expansion, now inaccurately 

 known, will be more correctly ascertamed by this research. 



The vibrations of tuning-forks received further investigation 

 by Prof. Mayer; the cost of inquiry was defrayed by the Bache 

 fund. The probable error in these determinations is the ji-j of 

 one vibration, i.e., with 256 vibrations to a second the probable 

 error is -r.-^,-,-, of a second. Differences in amplitude of vibration 

 make no difference in the vibratory period of the fork ; pressure 

 applied to the fork also has no effect on the vibratory period, 

 though it shortens the continuance of the note. 



Prof. Mayer also desciibed his investigations into the distri- 

 bution of magnetism in long bar magnets. Some ot these bars 

 which were tested were five feet in length. Various methods 

 have been tried for ascertaining the facts of magneiic distri- 

 bution ; Prof. Mayer gave due credit to other workers in this 

 field, and described their experiments. 



The Academy will hold its semi-annual meeting next autumn 

 at New York. 



NOTES 



The following is a list of the officers of the forty-seventh annual 

 meeting of the British Association which will, as we have intimated 

 commence at Plymouth on Wednesday, August 15 : — President 

 Elect— Prof. Allen Thomson, M.D., LL.D., F.R.S., F.R.S.E. 

 Vice-Presidents Elect — The Right Hon. the Earl of Mount- 

 Edgcumbe, D C.L., the Right Hon. Lord lilachford, K.C.M.G., 

 Dr. William Spoltiswoode, F.R.S., Dr. William Froude, C.E., 



F.R.S., Mr. Charles Spence Bate, F.R.S. General Secre- 

 taries— Capt. Douglas Gabon, C.B., F.R.S., Dr. Philip Lutley 

 Sclater, F.R.S. Assistant General Secretary — George Griffith, 

 M. A., F. C. S. General Treasurer — Prof. A. W. WilHamson, 

 F.R.S. Local Secretaries — Messrs. William Adams, William 

 Square, F.R.C.S., Hamilton Whitefore. Local Treasurer— Mr. 

 Francis Hicks. The Presidents of the Sections are as follow : — 

 .Section A : Mathematical and Physical Science — President, 

 Prof. G. C. Foster, F.R.S. Section B : Chemical Science — 

 President, F. A. Abel, F. R. S. Section C : Geology— President, 

 W. Pengelly, F.R.S. Section D : Biology — President, J. Gwyn 

 Jeffreys, F.R.S., F.L.S. Department of Zoology and Botany, 

 J. Gwyn Jeffreys, F.R.S., F.L.S. (President), will preside. 

 Department of Anatomy and Physiology, Prof. Macalister, 

 M.D. (Vice-President), wiU preside. Department of Anthro- 

 pology, Sir Walter Elliot, K.C.S.L, F.L.S. (Vice-Presi- 

 dent), will preside. Section E : Geography— President, Ad. 

 miral Ommanney, FR.S., F.R.G.S. Section F: Economic 

 Science and Statistics — President, the Right Hon. the Earl 

 of Fortescue. Section G : Mechanical Science — President, 

 Edward Woods, C. E. The reception room will be opened 

 on Monday, August 13, at I p.m., and on the follow- 

 ing days at 8 A.M., for the issue of tickets to mem- 

 bers, associates, and ladies, and for supplying information. 

 No tickets will be i:sued after 6 P..M. The first general 

 meeting will be held on Wednesday, August 15, at 8 P.M., 

 when Prof. Andrews, F.R.S., will resign the chair, and Prof. 

 Allen Thomson,; F.R.S., Pre-ident Elect, will assume the 

 Presidency,! and deliver an Address. On Thursday evening, 

 August 16, at S A.M., a soiree ; on Friday evening, August 17, 

 at 8. 30 P.M., a Discourse by Prof. Warington Smyth, M..\., 

 F.R.S., on the Physical Phenomena connected witli the Mines 

 of Cornwall and Devon ; on Monday evening, August 20, at 

 8. 30 P.M., a Discourse, but by whom not yet arranged; on 

 Tuesday evening, August 21, at S r.M, a soiree ; on Wednesday, 

 August 22, the Concluding General Meeting will be held at 

 2.30 P.M. The local arrangements for the Plymouth meeting 

 are not yet matured, but we believe they will include an exhi- 

 bition of paintings chiefly by artists of Devon and Cornwall, 

 including magnificent examples of Reynolds, Opie, Eastlake, 

 Northcote, Couke, Prout, &c. There will be excursions to 

 Torquay or Kent's Hole, &c., and the Dart; up the Tamar 

 or Cotehole ; to the Moss Clayworks and over Dartmoor ; to 

 the Eddystoue Breakwater and Government establishments ; to 

 amoUed glaaa .the Caradoc mines, the Land's End, &c. 



A RECEPTION was held by the President of the Royal Society 

 and Lady Hooker at Burlington House, on Wednesday evening 

 June 13, which was largely attended. The invitations included 

 ladies as well as men of science. The rooms were decorated with 

 plants, and there was a collection of instruments and objects ot 

 scientific interest. Among the novelties were new spectroscopic 

 instruments exhibited by Mr. Browning and Mr. Hilger ; and 

 Messrs. Tisley and Spiller's harmonograph curves, drawn on 

 smoked glass, two of which held together against a light give 

 some of the effects of polarised light. 



A Congress on Domestic Economy, organised by the Society 

 of Arts, is to be held in Birmingham on July 18 and 19. 

 Section A is to include (l) Needlework; (2) Cleanliness; (3) 

 Food and Cookery ; (4) Household Expenditure ; (5) Thrift. 

 Section B (6), Health; (7) Sickness; (8) The Dwelling; (9) 

 Warming and Ventilation. Section C (10), Teaching the Sub- 

 jects in Elementary Schools; (11) Text- books; (12) Inspection 

 and Government Grants ; (13} Importance of Female Inspectors; 

 (14) Examinations. A number of papers are already promised, 

 among them bemg papers by Mrs. W. E. Gladstone and Prof. 

 Huxley. The Local Committee includes the Lord.s- Lieutenant 



