!883-J Analyses of Boohs . 419 
fallen in price, and are so exclusively used in alum-making that 
it is now not easy to procure a sample of ammonia alum. 
Under “ Castor Oil ” we read that “ this oil is extracted from 
the seeds of Ricinus communis or Palma Christi, both of which 
are cultivated in warm climates.” Palma Christi is simply a 
synonym for Ricinus communis, not a distinct species of tree. 
Under “ Organic Matter ” we find a curious remark : — “ This 
term is often employed to designate varieties of non-volatile 
vegetable and animal substances of unknown composition, which 
are prone to change by absorption of oxygen. Bodies which have 
a definite formula, however, are often included in the class of 
organic matters if they readily pass by oxidation into ill-defined 
products. But a stable vegetable acid like acetic acid, or a neu- 
tral substance not readily oxidisable, such as glycerine, although 
really organic in composition, would not usually be referred to by 
this term.” We certainly have never heard the term “ organic 
matter” applied exclusively or preferentially to unstable bodies 
or such as are of indefinite or unknown composition. If such a 
usage exists, the author would have done well to have pointed 
out its impropriety. 
On page 93 we read that “ solutions of the sulphocyanides of 
ammonium or potassium- have been recommended for fixing po- 
sitive photographs instead of hyposulphite of soda ; but it is 
doubtful whether any advantage is gained.” But on page 149 it 
is stated that the sulphocyanides “have the advantage of im- 
parting no sulphur to the print, and they preserve the tones clear 
and free from mealiness.” 
As regards the purely photographic or the practical portion of 
the book before us, there can be no doubt that it fully merits the 
reputation which it has all along enjoyed. In case of a new 
edition, which may be looked forward to as a matter of certainty, 
we should suggest a revision of the earlier or introductory 
chapters. 
Transit Tables for 1883. Giving the Greenwich Mean Time of 
the Transit of the Sun and of certain Stars, for every Day 
in the Year; with an Ephemeris of the Sun, Moon, and 
Planets, and other Information, computed from the Nautical 
Almanac for Popular Use. By Latimer Clark, M.I.C.E., 
&c. London : A. J, Frost. 
This work gives instructions in the art of obtaining correct time 
in any part of the world by means of the transit instrument. 
The Preface explains the use of this important astronomical in- 
strument, and the method of its adjustment. For this purpose 
it is merely needful to choose an open site facing southwards, to 
