Silvanus P. Thompson

The Inventor of the Nicol Prism

CAN any of your readers supply me with the dates of birth and death of William Nicol, the inventor of the Nicol prism? There is a tablet to his memory in the Wariston Cemetery, in Edinburgh, bearing an inscription drawn up by the late Prof. Tait. Strange as it may seem, though his fame is world-wide in optics, he is not even mentioned in the “Dictionary of National Biography,” nor do I know of any memoir of him elsewhere.

A Cheap Insulating Support

INSULATING-SUPPORTS are so indispensable in the work of an electric laboratory that several forms have come into extensive use. The plan devised by Sir W. Thomson for securing high insulation by surrounding a glass stem with concentrated sulphuric acid to absorb the moisture which otherwise would condense from the air and form a conducting film over the surface of the glass is remarkably efficient, and has many advantages. Modifications of this form of insulator have been largely used by Prof. Clifton, F.R.S., in the Clarendon Laboratory, and by Profs. Ayrton and Perry in the laboratories of the Technical College at Finsbury. Another modification due to M. Mascart, was described in NATURE, vol. xviii. p. 44; and this pattern has come into extensive use under the name of the support isolant Mascart. Though excellent in every way it is very expensive, as its manufacture necessitates a special piece of glass-blowing. The central support of glass is solidly fused into the bottom of a glass vessel with a very narrow neck into which acid is poured through a tubulure at the side.

Faraday's “Experimental Researches”

DOUBTLESS many of your readers will have observed an advertisement of a well-known antiquarian bookseller professing to be able to supply “a perfect copy” of Faradays “Experimental Researches” at a price not too exorbitant for a complete original copy of that priceless work.

A NEW GALVANOMETER FOR LECTURE PURPOSES

ALL who have had the experience of attempting to exhibit to a large audience the simple phenomena of dynamical electricity will bear testimony to the difficulty of rendering apparent over the whole of a lecture-theatre the movements of a galvanometer needle. When the galvanometer lies flat upon the table and the movements of the needle itself, or of the index attached to it are observed, the number of observers must be confined to those near at hand. Even the mirror galvanometer, indispensable as it is for delicate experiments, is open to the objection that a popular audience does not immediately appreciate the significance of the motions of the wandering spot of light. The devices for projecting the moving needle upon the screen have, up to the present time, been so large and inconvenient as to militate against their use for popular demonstration.

Oersted and the Electric Theory of Light

IN Sir John W. F. Herschels classical article on light (dated 1827) in the “Encyclopedia Metropolitana” of 1830, p. 439, there is a vague reference to a theory of light then recently propounded by Oersted, in which he sought to explain the nature of light-waves as a succession of minute electric sparks. Desiring to follow up this reference, the writer of this notice consulted, but fruitlessly, all the writings of Oersted within his reach. Thereupon he applied for information to Prof. Absalon Larsen, of Copenhagen, who, after consultation with Prof. Christiansen, kindly directed the writer to sources not available in London, and furnished the extracts now given from Oersteds writings.

Prof. Alfred Cornu

CORNU was born in 1841 at Châteauneuf, and entered the great military school of Paris, the École Polytechnique, at the age of nineteen. After four years of study there he entered the Ecole des Mines, which he quitted in 1866, thus completing a brilliant career as a student. One year later, at the age of twenty-six, he was chosen as professor of physics at the École Poly technique, a post which he filled to the end of his life and adorned with the many results of his scientific researches.

The Late Prof. Tennant on Magic Mirrors

SEVERAL scientific friends tell me that the late Prof. Tennant, the well-known mineralogist, published some twenty or twenty-five years ago a small pamphlet on Magic Mirrors. Failing to find a copy even in the library of Kings College, I invite the readers of NATURE to assist me to discover one.

Printing Mathematical Symbols

EVERYONE who has had to correct printers proofs of mathematical formulæ must be painfully alive to the pitfalls into which the non-mathematical compositor continually blunders. To such as know the extreme difficulty of getting such formulæ properly set up, there have doubtless occurred from time to time suggestions for such simplifications of notation as shall render the composition less liable to derangement. One most sensible step of the kind I allude to is the introduction by Sir G. Stokes of the solidus notation for quotients, whereby

Height of T'ai Shan

A FORMER student of mine, Mr. S. Couling, has recently ascended Tai Shan, the loftiest of the sacred mountains of China, and one of the most ancient and popular places of pilgrimage. He believes that the height of it above the surrounding plain has never before been measured, and has sent me his observations to reduce. The elevation from the plain to the summit comes out at 4780 feet; whilst a temple vaguely stated to be about 400 feet below the summit is, as ascertained by barometer, 4485 feet above the plain.

Electricity and Clocks

THE exact combination about which Mr. Wilson inquires is already in existence: it can be seen at 2, Garfield Buildings, Grays Inn Road, in the Jensen electric bell factory. The arrangement used by Mr. Jensen—and it seems to me preferable to that suggested by Mr. Gardner—is to cause the hammer of the small clock to make electric contact in the circuit of the distant large bell as it rises in preparation for striking the blow upon its own small bell. Wih a rubbing contact the action is perfectly certain.