884 
electromotive force, but when the circuit is in 
advance of the electromotive force an increase 
of frequency decreases the reactance. 
The author points out that the terms virtual 
and effective are employed indiscriminately by 
some writers, but has been unsuccessful in his 
attempt to make the termsclear. The effective 
value of the EH. M. F. is taken to be its compo- 
nent of direction of the current; the effective 
current is the component of current in the direc- 
tion of the E. M. F., all of which is quite be- 
yond criticism, unless it be one of words. ‘ Vir- 
tual value’ is adopted to designate the square 
root of the mean square value and is properly 
explained to be the equivalent of a direct electro- 
motive force or current which would produce 
the same effect either on an electrostatic volt- 
meter, or in heating. Thus, we may have oc- 
casion to refer to the virtual value or to the 
maximum value of any quantity, as of the im- 
pressed E. M. F., of the effective H. M. F., of 
the total current, or of the effective current. 
Although thus clearly giving a proper meaning 
to the term virtual, the author usually employs 
‘virtual E. M. F.’ as synonymous with ‘im- 
pressed EK. M. F.,’ and ‘virtual current’ as be- 
ing the total or actual current which flows as 
distinguished from a particular component of it. 
Thus (p. 83), ‘‘In most circuits the impressed 
or virtual E. M. F. meets with an opposing 
i. M. F. of reactance, and the effective E. M. F. 
is something less than the virtual E. M. 
F. * * *”” Also (p. 84), ‘‘That proportion of 
the current which can do useful work may be 
called the effective current. When there is no 
phase difference, the effective current is the 
same as the virtual current; but as the angle 
of lag or lead increases, so does the value of 
the effective as compared with the virtual cur- 
rent diminish.”’ Again (p. 87), the author re- 
fers to ‘impressed or virtual electromotive 
force.’ 
These two much abused words are likewise 
unnecessarily dragged in; thus (p. 64) we note 
“virtual or effective resistance ;’ (pp. 89 and 93), 
effective watts,’ the imputation being that we, 
might likewise have ineffective watts! Also 
(p. 94) we are told that the virtual watts put 
into a circuit may be far in excess of the actual 
power conveyed ! 
SCIENCE. 
[N.S. Voz. VI. No. 154. 
Throughout the book the author has used 
terms with meanings other than those he has as- 
signed to them by definition. 
These blemishes are serious ones. With thor- 
ough revision, the book will satisfactorily meet 
the admirable end the author had in view. 
FREDERICK BEDELL. 
Anleitung zur Mikrochemischen Analyse der wich- 
tigsten organischen Verbindungen. Von H. 
BEHRENS, Professor an der Polytechnischen 
Schule zu Delft. Viertes Heft. Karbamide 
und Karbonsaeuren. Mit 94 Figuren im 
Text. Hamburg und Leipzig, Verlag yon 
Leopold Voss. 1897. Pp 129. Mark 4.50. 
In the first number of Professor Behrens’ book 
the anthracene group, phenols, quinones, ke- 
tones and aldehydes were considered. Thesec- 
ond number, treating of fibrous materials, was. 
reviewed in this JOURNAL for January 15, 1897. 
The third number deals with aromatic amines, 
and with the present number continues the: 
work satisfactorily. It should be remembered 
that Professor Behrens’ work is the only text- 
book extant in this important field. 
E. R. 
Die Chemie im téglichen Leben. Von DR. LASSAR- 
CoHN. Universitats Professor zu Konigs- 
berg. Zweite Auflage. Hamburg und Leip- 
zig, Verlag von Leopold Voss. 1897. 
The first German edition of Professor Lassar- 
Cohn’s book was fully reviewed in this JoURNAL 
for January 22, 1897, by Professor Orndorff. 
The appearance of a second German edition, 
and the success of Professor Pattison-Muir’s. 
English translation show the value of the book. 
E. R. 
SOCIETIES AND ACADEMIES. 
THE NEBRASKA ACADEMY OF SCIENCES. 
THE eighth annual meeting of the Academy 
was held at Lincoln on November 26th and 27th. 
On the first day the Presidential address was: 
given by Dr. A. S. von Mansfelde, of Ashland, 
his subject being ‘Some Practical Applications 
of Science.’ It was devoted largely to a dis- 
cussion of the alcohol question from the scientific 
and medical point of view in opposition to many 
untenable positions taken by advocates of total 
abstinence. 
