78 Literary Notices. 



thallium, as illustrated in thallic alcohol, suggested the application 

 of that metal to the production of a very dense, and therefore highly 

 refractive glass ; and experiments made on the subject have been 

 extremely successful. Difficulties of a serious character were en- 

 countered at first, the glass produced being fibrous, and not very 

 transparent ; but these have been overcome by the assistance of M. 

 Eeil, a glass manufacturer of great experience, and a thallic glass 

 in every respect suited to optical purposes has been obtained. 

 When carbonate of thallium is employed in its manufacture, its 

 tinge is yellowish ; but if this is considered an objection, the sub- 

 stitution of sulphate for the carbonate affords a perfectly colourless 

 result. Thallic glass is the most dense, and the most highly refrac- 

 tive and dispersive known. 



Magnetism and Diamagnetism op Gases and Vapours. — A simple 

 and effective experiment by which the magnetism and diamagnetism 

 of gases and vapours may be rendered visible to a large audience 

 has long been sought for, and has at length been discovered. It 

 consists in blowing a bubble at the end of the stem of a clay 

 tobacco-pipe, the gas used for inflation being oxygen, and the fluid 

 a solution of soap mixed with glycerine, which affords a bubble 

 that lasts a considerable time. The bubble is placed above the 

 poles of an electro-magnet, and at very small distance from them. 

 When a current is sent through the coil of the electro- magnet the 

 bubble is attracted, and if the circuit is completed and broken 

 several times in succession, a very striking oscillation of the bubble 

 will be produced. If magnesium is burned over the pole of an 

 electro-magnet to which a conical form has been given, when the 

 circuit is complete, the smoke will be divided laterally, and assume 

 the form of the letter U. 



LITERARY NOTICES. 



The Constellation-Seasons : An Easy Guide to a Knowledge of 

 the Stars. Exhibiting, in Twelve Planispheres, the Appearance of 

 the Heavens at any Hour of the Night, all the Tear round. By 

 Richard A. Proctor, BA., E.R.A.S. (Longmans.) — Mr. Proctor 

 has produced one of the most useful series of maps we have seen 

 for the purpose he had in view, namely, enabling students to learn 

 the position of the chief stars and constellations at various periods 

 of the year, or to recognize them at any time. " Each map," he tells 

 us, " contains the whole of the visible heavens at the hour and date 

 mentioned beneath it ; the centre of the map is the point over the 

 observer's head at the time named ; the outline of the map is the 

 observer's horizon ; each star is placed in its proper direction as 

 respects the compass-points (marked in round the map) ; and each 

 star is placed at its true proportionate distance from the centre." 

 Eor the teaching of young people, and for adults who wish to know 

 the position of particular stars at certain dates, these maps will be 



