404 SCIENTIFIC EECORD FOR 1882. 



ence than a deflection of the needle of ordinary instruments and 

 a corresponding movement of the armature of the Morse ink-writer 

 and sounder, so that unless a sharp outlook be kept with the eye con- 

 stantly directed to the instrument the actual time of the signal may 

 be lost, perhaps also to be lost again on the following day through 

 similar accident. By the new instrument, however, the instant the 

 current is sent the needle on its dial is deflected, and simultaneously 

 a bell rings and continues to ring as long as the current is passing; the 

 index needle, or, in other words, the needle of the galvanometer, which 

 is the principal feature of the invention, when deflected, presses against 

 a small spiral spring surrounding the stops or ivory jnns on the dial 

 plate, and by this contact the galvanometer forms itself into a " relay '^ 

 and brings a local battery in circuit with the bell, which is contained 

 in the same instrument, so that when the first jiart of the time signal is 

 sent the needle is deflected and at the same moment the bell rings j 

 thus attention to the time is at once arrested. It should be mentioned 

 that the resistance to the line, although low, is intended to be inserted 

 only during the transmission of the time signal, as by means of what 

 is generally termed a " switch " the instrument is put on and ofl' the 

 circuit at will, and employed only during the time set apart for the 

 transmission of the Greenwich time signal. However feeble the cur- 

 rent may be, the galvanometer is so sensitive that a deflection of its 

 needle is absolutely certain, whilst the bell cannot fail to answer to the 

 power of its local battery. We are informed that not only is Messrs. 

 Francis & Co.'s new instrument capable of doing what we have already 

 stated, but it may be available for communication from different parts- 

 of the building, an advantage which is certain to be recognized and 

 approved by many conducting large business establishments, where the 

 saving of time in conveying messages and giving orders is a matter 

 which is frequently of great importance. {Nature, February 10, 1881, 

 XXIII, p. 347.) 



R. A. Smith has devised a new actinic process by means of which he 

 hopes to investigate the absorbing power of the atmosphere and other 

 gases. From some preliminary remarks we extract the following: The 

 fundamental idea is that when iodide of potassium in solution is treated 

 with nitric acid, so small in quantity as to cause no change of color in 

 dull diffused light, a change takes places when the same mixture is 

 brought into clear light — iodine is set free and the solution becomes 

 yellow. The amount of iodine freed can be triturated with great ex- 

 actness by the use of hyposulphite ; this constitutes the whole process. 

 Some slight allowance for time and temperature may have to be made. 

 After giving a few samples of experiments with iodide of potassium 

 triturated with nitrogen. Dr. Smith says: "There seems, therefore, no 

 reason to doubt that this is a true i)hotometric process, with special 

 capacities to be developed in time. I may add that I did obtain better 

 results at the window of my house than at the observatory at the same 



