Intelligence and Miscellaneous Articles. 547 



most is to call the attention of enlightened teachers to a truly 

 educative manual, which is no mere collection of dry bones, but 

 alive with suggestion, and interest, and insight. 



Transit Tables for 1886. By Latimer Clark, F.R.A.S., M.I.C.E. 

 London: Spon. (Pp.71.) 



These Tables constitute a multum in jparvo for the use of those 

 who do not care to turn over the pages of the bulky Nautical 

 Almanac. Mr. Clark has added to the usefulness of his previous 

 issues by appending the Eight Ascensions of what he calls 

 11 Additional Stars," as well as the time of the Moon's southing on 

 every alternate day of the year. He has also reverted to his 

 original plan of giving the times of transit to hundredths of a 

 second. 



With the aid of this handy volume and one of the excellent 

 Transit Instruments, invented by the Author, the merest amateur 

 will be able to keep his clocks goiug in accordance with Greenwich 

 or his own local time. 



LXIV. Intelligence and Miscellaneous Articles. 



VISIBLE REPRESENTATION OF THE FOCUS OF ULTRA-RED RAYS 

 BY PHOSPHORESCENCE. BY E. LOMMEL. 



A WELL-KNOWN experiment for making the ultra-red rays 

 - ^ visible is that of Tyndall. He uses a lens obtained by 

 filling a spherical flask with a solution of iodine in bisulphide of 

 carbon. This solution is opaque to the ordinary rays, but trans- 

 mits the ultra-red rays and concentrates them in a focus ; the in- 

 creased heating effect in this point is shown by the ignition of 

 tinder or gun-cotton, or the incandescence of platinum. 



This focus can easily be made visible by means of certain phos- 

 phorescent substances. Balmain's luminous paint is well adapted 

 for the purpose; or, still better, a greenish-blue phosphorescent 

 calcium sulphide, the properties of which I have already described*. 

 If this has been made slightly phosphorescent by ordinary daylight, 

 it is increased to a bright luminosity by the less refrangible, and 

 particularly by the ultra-red rays ; and when the radiation is mode- 

 rately strong this lasts for hours, and even after the radiation 

 ceases it gradually diminishes, but is visible for some time. After 

 this cessation a dark spot appears on the irradiation place, because 

 here, in consequence of increased emission, the luminous power is 

 diminished or entirely destroyed. 



If a transparent screen be m r de of this substance by spreading a 

 layer of the powder between two glass plates cemented at the edges, 

 the ultra-red region of the spectrum may be shown in greenish- 

 blue phosphorescence near the red end of the spectrum, both on 

 the front and back of the glass. 



The same screen can be used to render visible the dark focus . 



* Wiedemann's Annalen, vol. xx. p. 853. 



