I878.J 
559 
Notices of Books . 
We will not here objedl that the atomic weight of oxygen is 
considered to be not 16, but 15*96, and that of carbon not 12, 
but 11*97. But we must certainly enquire whether Dr. Mac- 
vicar assumes it as a general truth that if the atomic weight of 
an element equals the sum of the atomic weights of certain 
other elements, it is to be considered as capable of resolution 
into the latter ? We shall be ready to accept the author’s view 
of the composition of silica so soon as he shall have succeeded 
in resolving it into oxygen, carbon, and hydrogen, or in forming 
it synthetically by the union of these elements. 
Concerning ammonia the author entertains also peculiar 
views. He writes :■> — “ The experimental chemist experiences 
no greater difficulty in his pursuit of exacft analysis than to 
obtain possession of a considerable .quantity of mere or pure 
water. Let him distil water over and over again, if only the 
distillate have stood for a time he finds ammonia in it. This 
phenomenon the popular chemistry which maintains the solidity, 
simplicity, and non-developable character of the sixty-three 
chemical atoms, is obliged to ascribe to the previous existence 
of organic matter in the water.” This state of things, which he 
thinks “ cannot but be provoking to the chemist,” he accounts 
for by pronouncing ammonia <£ a produdt of pure water itself, 
and immediately after common vapour itself a primeval sub- 
stance.” Before Dr. Macvicar exults over the “ popular che- 
mistry ” let him remember that ammonia is not difficult to detecT 
in the atmosphere, and cannot well escape being absorbed by 
water on prolonged standing, even if preserved in bottles with 
the best-fitting stoppers. Can he bring forward a case where a 
competent experimentalist has obtained water free from ammo- 
nia and from organic matter, has then sealed it up before the 
lamp, and has then on opening it — after the lapse, say, of a 
year — found it ammoniacal ? If the author can make ammonia 
out of water, not merely honour will be his, but wealth such as 
the world has not yet dreamt of. Will he neither tell us how it 
is to be done, nor, if that is impossible, point out where Nature 
is doing it in “ a considerable quantity ” ? 
It will have been perceived that Dr. Macvicar does not recog- 
nise the ordinary elements. He says — “ There are between 
sixty and seventy (kinds of) particles of matter which chemists 
down to the present day have not succeeded in decomposing, 
and which, strange to say, on this negative evidence they have 
concluded to differ from all the thousands of other (kinds of) 
particles which in the progress of analytical chemistry they have 
succeeded in decomposing, and hold to be simple and solid 
unities or true natural atoms of matter.” 
The author must surely be aware that the definition of an 
element, in chemical language, is merely a body which we have 
neither been able to compose nor to decompose. “ Strange to 
say ” he goes on to show why these elements should “ differ 
