1879 -] 
Notes. 
267 
greatly increased its utility. The cavity, instead of being con- 
cave as usual, is ground out, as shown in the cut, having the 
greatest depth at the edges, the bottom of the cell being convex. 
A drop of water is held by capillary attraction between ths 
cover and the projection ; the cover may be fastened or not, at 
pleasure, 
A writer to “ Science Gossip ” describes a Very simple live box, 
constructed of two ordinary 3X1 slides, placed between two easily 
fitting flattened brass bands. The slides are kept apart by an 
india-rubber ring of any convenient thickness, and the whole 
contrivance kept tight by means of wedges. The contrivance is 
readily constructed, and applicable to many purposes where a 
thin glass in front is not required. 
The inhabitants of Heilbronn, the native town of the late Dr. 
Julius Robert Mayer, so renowned for his contributions to the 
Mechanical Theory of Heat, have resolved to erect a suitable 
memorial on the spot where he lived, laboured, and died. The 
following gentlemen have agreed to form an English Mayer- 
Memorial Committee : — William Spottiswoode, Esq., Pres. R.S.; 
Sir Joseph Hooker, K.C.S.I., V.-P.R.S. ; Prof. Stokes, Sec. R.S. ; 
Prof. Huxley, Sec. R.S. ; Prof. Tyndall, F.R.S. ; Dr. William 
Siemens, F.R.S. ; Herbert Spencer, Esq. ; Sir William Gull, 
Bart., F.R.S.; Sir James Paget, Bart., F.R.S.; Sir John Lub- 
bock, Bart., F.R.S.; Prof. Henry Smith, F.R.S.; Dr. Debus, 
F.R.S.; George Busk, Esq., F.R.S.; Dr. Hirst, F.R.S.; Prof. 
Frankland, F.R.S.; Prof. Dewar, F.R.S.; John F. Moulton, 
Esq., M.A. ; Frederick Pollock, Esq., M.A. Subscriptions ex . 
ceeding one pound may be sent by cheque to Messrs. Robarts, 
Lubbock, and Co., 15, Lombard Street. Smaller sums may be 
sent by post-office order to the Honorary Secretary, T. Archer 
Hirst, Royal Naval College, Greenwich. 
Chemistry and Technology. 
The substance of which the much-talked-of Swiss “ self- 
luminous clock-dials ” are composed has, according to “ The 
Engineering and Mining Journal,” been examined by Prof. Henry 
Morton, of the Stevens Institute of Technology, Hoboken, and 
has been ascertained to be the “ sulphide of calcium,” which is 
caused to adhere to the dial surface by means of some resinous 
varnish. This compound has long been known to possess phos- 
phorescent qualities of a high order; but as prepared for this 
special use its phosphorescence has never before been equalled, 
