Notices respecting New Books. 459 



tufts of a white, finely crystallized substance. All the various 

 parts disengaged ammonia when fused with potash. 



The mass still contained unchanged silicon : this was removed 

 by treating it with chlorine, which converted it into chloride of 

 silicon without altering the nitride of silicon. 



When this nitride of silicon was heated in a stream of aqueous 

 vapour and carbonic acid, it was slowly decomposed with forma- 

 tion of carbonate of ammonia and amorphous silica. Nitride 

 of silicon, prepared from the chloride, is decomposed by water at 

 the ordinary temperature. 



When crystals of silicon are heated in an atmosphere oi moist 

 chlorine, they are changed into pseudomorphs of silica. 



Next to oxygen, silicon occurs to the greatest extent in nature ; 

 and it is surprising that it does not occur in the free state, inas- 

 much as it is not oxidized by oxygen even at a white heat. As 

 the above experiment shows, it unites directly with nitrogen. 

 If we may adopt a geological fancy, we might suppose that at 

 the period of the formation of our planet, when the elements 

 combined to form the compounds which now constitute its crust, 

 the silicon combined with the nitrogen, and the ignited nitride 

 of silicon coming in contact with water, was decomposed into 

 silica and ammonia. In this manner ammonia was formed, by 

 which, on the first occurrence of vital organisms, nitrogen was 

 introduced into organic compounds. 



LXXI. Notices respecting New Books. 



Practical Geometry. By II. Burchett, Head Master of the Training 

 and National Schools (in connexion with the Science and Art De- 

 partment). Third Edition. 1859. Chapman and Hall, 193 Pic- 

 cadilly. 



THIS book contains the course of instruction given to the Mas- 

 ters in training for schools in connexion with the department 

 of Science and Art, at the Trahnng School, Marlborough House, 

 and is also the text-book used by Her Majesty's Inspectors in their 

 examinations of the training colleges throughout the country. The 

 book bears on its title-page the stamp of the Committee of Council 

 of Education, and it is issued as a prize to pupil teachers. It is 

 further worthy of observation, that this treatise is the only work in 

 which the Department of Art professes to give exact ideas on geo- 

 metrical constructions. A book so patronized should surel3^ at the 

 very least, be niatliematically correct. Now it almost passes belief, 

 that this book, so glorified, and occupying so important a place in 

 relation to the education of the country, contains not a few propo- 

 sitions which are absolutely false ! The following propositions, for 



