118 Notices of Books. (January, 
perusal of Dr. Althaus’s book, and to express congratulation 
upon the attaining of a third edition. But not only will the 
reader in search of medical knowledge find here what he re- 
quires, but the general electrician will find also complete record 
of observations as to the action of electricity upon physiologically 
organic substances. 
A Treatise on Acoustics in Connection with Ventilation, and an 
Account of the Modern and Ancient Methods of Heating 
and Ventilation. By ALEXANDER SAELTZER, Architect. 
New York: D. Van Nostrand. 
Mr. SAELTZER has given his subject great attention, and this 
attention has led him to some highly original views upon the 
relation of the propagation of sound to the density of the air, 
and the propagation of sound waves across strata of different 
density. Given the air and the propagation of sound waves 
across strata of different density, the author shows how it is 
that the voice of a speaker, whether proceeding from pulpit, 
platform, or proscenium, may be so reflected by the surface of 
the different air-strata as to be inaudible or confused to the 
hearers above or below the strata in which he speaks. Mr. 
Saeltzer next recounts the experiments that have led him to 
adopt certain principles of ventilation as aids in developing the 
acoustical properties of public buildings, by breaking up the 
air-strata. The book should be read, not only by the architect, 
but by every professional man whose duty it is to speak in public. 
Experimental Research on the Causes and Nature of Catarrhus 
Estivus (Hay-Fever, or Hay-Asthma). By C. H. BLacktey, 
M.R.C.S. Eng. London: Bailliére, Tindal, and Cox, 
King William Street, Strand. 
Mr. Blackley may be fairly congratulated on having produced 
a work which is not merely a valuable contribution to our medical 
literature, but which will be read with interest by many scientific 
men not connected with the profession. 
Long-Span Bridges. By B. Baker, Assoc. Inst. C.E. Revised 
Edition. London: E. and F. N. Spon. 1873. 
To the student or to the engineer who desires to investigate the 
comparative theoretical and practical advantages of the various 
adopted or projected types of bridge construction, whether in- 
cluding box-plate, lattice, or bowstring girders, ribs, or sus- 
pension, we cordially commend this little work, as readable as it 
is accurate. The work really includes two sections, relating 
respectively to long- and to short-span bridges, and is illustrated 
with diagrams of type form built upon the long-span system. 
