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Taw Sien-Ko. A Preliminary Study of the Kalyani Inscriptions of Dhammacheti, 1476 A.D. 4to. Bombay 1893.

Department of Revenue and Agriculture, Calcutta.

March 8, 1894.

Sir JOHN LUBBOCK, Vice-President, in the Chair.

A List of the Presents received was laid on the table, and thanks ordered for them.

The Croonian Lecture was delivered as follows:

CROONIAN LECTURE.-“ La fine Structure des Centres Nerveux."

By S. RAMÓN Y CAJAL, Professor of Physiology in the
University of Madrid. Received March 1, 1894.

[Publication deferred.]

Presents, Varch 8, 1894. Transactions. Batavia :-Bataviaasch Genootschap van Kunsten en Weten. schappen. Notulen. Deel XXXI. Aflev.

1-2. Svo. Batavia 1893; Tijdschrift voor Indische Taal-, Land- en Volkenkunde. Deel XXXVI. Aflev. 4-6. 8vo. Bataria 1893.

The Society. Buitenzorg :—'s Lands Plantentuin. Verslag. 1892. 8vo. Bataria 1894.

The Director. Gloucester:-Cotteswold Naturalists' Field Club. Proceedings.

Vol. XI. Part 1. 8vo. Gloucester (1894). The Club. Heidelberg :-Naturhistorisch-medicinischer Verein. Verhandlungen. Bd. V. Heft 2. 8vo. Heidelberg 1894.

The Society. Lausanne :-Société Vaudoise des Sciences Naturelles. Bulletin Vol. XXIX. No. 113. 8vo. Lausanne 1893.

The Society. London :- British Astronomical Association. Journal. Vol. IV. No. 3. 8vo. London 1894,

The Association, East India Association. Journal. Vol. XXVI. No. 3. 8vo. London 1894.

The Association. Geologists' Association. List of Members. 1894. 8vo. London.

The Association. Transactions continued).

Iron and Steel Institute. Journal. Vol. XLIV. 8vo. London 1894.

The Institute. Photographic Society of Great Britain. Journal and Transactions. Vol. XVIII. No. 6. 8vo. London 1894.

The Society Royal Microscopical Society. Journal. 1894. Part 1. Svo. London.

The Society. Saint Bartholomew's Hospital. Reports. Vol. XXIX. 8vo. London 1893.

The Hospital Madison :-Wisconsin Academy of Sciences, Arts, and Letters. Transactions. Vol. IX. Part 2. 8vo. Madison 1893.

The Academy. New York :-American Museum of Natural History. Bulletin. Vol. V. Vol. VI. Pp. 33—80. 8vo. New York 1893–94.

The Museum. Rome :-R. Comitato Geologico d'Italia. Bollettino. Vol. XXIV. Trim. 4. 8vo. Roma 1893.

The Committee. Washington :-National Academy of Sciences. Memoirs. Vol. VI. 4to. Washington 1893.

The Academy.

Observations and Reports.
Hobart :-Office of the Government Statistician. Statistics of the
Colony of Tasniania. 1892. Folio. Hobart 1893.

The Government Statistician. India :-Botanical Survey. Records. Vol. I. Nos. 1-2. 8vo. Calcutta 1893–94.

The Survey. Geological Survey. Records. Vol. XXVI. Part 4.

8vo. Calcutta 1893.

The Survey Montpellier :-Commission Météorologique de l' Hérault. Bulletin Météorologique. Année 1892. 4to. Montpellier 1892.

The Commission. San Fernando :-Instituto y Observatorio de Marina. Observa

ciones Meteorológicas y Magnéticas. Año 1892. 4to. San Fernando 1893.

The Institute. Spain :-Comisión del Mapa Geológico. Boletin. Tomo XIX. 8vo. Madrid 1893.

The Commission.

Agricultural Gazette of New South Wales. Vol. IV. Part 12.

8vo. Sydney 1893. Department of Agriculture, Sydney. Horological Journal. Vol. XXXVI. No. 427. 8vo. London 1894.

British Horological Institute.

Journals (continued). Journal of Comparative Neurology. September, 1893. 8vo. Granville, Ohio.

The Editor, Stazioni Sperimentali Agrarie Italiane. Vol. XXVI. Fasc. 1. 8vo. Modena 1894.

R. Stazione Agraria, Modena.

Akerblom (Ph.) De l'Emploi des Photogrammètres pour mesurer la Hauteur des Nuages. 8vo. Upsala 1894.

Meteorological Observatory, Upsala. Basset (A. B.), F.R.S. [Volume of Excerpts lettered “Mathematical Papers, 1882-92."] 8vo.

The Author. Bickerton (A. W.) A New Story of the Stars. 8vo. Christchurch, N.Z. 1894.

The Author. Chijs (J. A. van der.) Dagh-Register gehouden int Casteel Batavia

vant passerende daer ter plaetse als over geheel NederlandtsIndia. Anno 1664. 8vo. Batavia 1893; Nederlandsch-Indisch Plakaatboek, 1602–1811. Deel XI. 8vo. Batavia 1893.

Bataviaasch Genootschap van Kunsten en Wetenschappen. Liversidge (A.), F.R.S. On the Origin of Moss Gold. [And other Papers.] 8vo. [Sydney 1893.]

The Author. Macfarlane (A.) On the Definitions of Trigonometric Functions. 8vo. Boston 1894.

The Author. Packard (A. S.) Further Studies on the Brain of Limulus Poly

phemus, with Notes on its Embryology. 4to. [Washington 1893.]

The Author.

March 15, 1894.

The LORD KELVIN, D.C.L., LL.D., President, in the Chair.

A List of the Presents received was laid on the table, and thanks ordered for them.

The following Papers were read :

I. “ The Thermal Radiation from Sun Spots. Preliminary

Notes of Observations made at Daramona, Streete, Co. Westmeath, 1893.” By W. E. WILSON, M.R.I.A. Communicated by G. JOHNSTONE STONEY, F.R.S. Received

January 4, 1894. These observations were made by means of a large heliostat, lent by the Royal Society, and a Boys's radio-micrometer. The heliostat consists of a plane silver-on-glass mirror of 15 in. aperture. It is mounted equatorially, and driven by a clock. When in use, it is adjusted to reflect the sunlight to the north pole, and, as long as the driving clock is kept in motion, the beam of light remains fixed in that position. In the track of this beam, and about 12 ft. from the plane mirror, is mounted a concave silver-on-glass mirror of 9 in. aperture, and about 13 ft. focus. Its axis points to the south pole, so that the cone of rays formed by it strikes the centre of the plane mirror, and a short distance inside the focus. A small plane mirror mounted on the end of an arm is then so placed as to intercept the cone of rays, and reflect it horizontally into the observatory window; an achromatic lens enlarges the solar image which is formed on a screen in the room to 4 ft. in diameter.

Behind this screen, and standing on a pier of concrete, is mounted the radio-micrometer. The aperture through which radiant heat reaches the sensitive thermo-coupie is a round hole drilled through a thick sheet of brass, and is only 1 mm. in diameter. A white card. board screen is placed in front of the brass one to cut off heat from falling on the latter, and is provided with a hole slightly larger. A beam of lime light is thrown on the mirror of the radio-micrometer, and reflected on to the scale in the usual way. The diagonal mirror of the heliostat is provided with slow motions in two directions, which are moved by long rods and Hook joints inside the observatory. Thus any part of the sun's disc can be placed on the small aperture of the radio-micrometer, and the driving clock will then keep it there.

The observations are taken in the following manner. A small screen is placed over the aperture of the radio-micrometer, and the zero position of the spot of light on the scale noted. The screen is then removed, and the umbra of a sun spot placed on the aperture. The reading is then taken and entered in column u. The image is then moved, so that a part in the neighbourhood of the spot, but at the same distance from the centre of the solar disc, is placed on the aperture. This reading is entered in column N. Finally, a reading is taken at the centre of the disc, and entered in column C. The throws of the instrument are then got by subtracting the figures in columns u, N, and C from the zero. The deflections of the instru. ment have been experimentally proved to be strictly proportional to the amount of radiant heat falling on the thermo-couple. The following is a typical observation taken August 7, 1893, of a large sun spot then visible. The umbra of this spot measured 0.8 in. across on the screen, so that the aperture of the radio-micrometer was only covering about coo of the apparent area of the umbra.

[blocks in formation]

umbra of spot

1:31 The ratio

= 0.292. neighbouring photosphere 4:49 Five concordant readings gave a mean deflection of 4:57 for the

umbra centre of the sun, which gives for the ratio = 0.287.

centre This spot was at a distance from the centre of the disc of about 0-4 of the radius.

As the radiation from the photosphere falls off from the centre to the edge of the disc, it seemed an interesting point to determine if any change in the ratio of u/C would take place as a spot was carried across the disc by the sun's rotation. If the spot is, as is generally thought, a depression, the absorption of heat ought to increase as it is carried towards the limb, on account of the increased

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