il SCIENCE —AD VERTISEMENTS. 
RARE MINERALS. 
THAUMASITE, from Paterson, N. J., asulphate, silicate and 
carbonate of calcium, pure white, 25c. 
EKDEMITE, bright yellow on red wulfenite, Arizona, 50c. 
NATIVE ARSENIC, Japan, 14 to 34-inch ecrsytallized balls 
25c, 35c. 
Collections for Schools. 
ALPHA COLLECTION, twenty-five specimens in trays, con- 
tained in a neat wooden box and accompanied by a 46- 
page guide book (XIII., Guide for Science Teaching, Bos- 
ton Society of Natural History), Price, complete, $1.00. 
CABINET COLLECTIONS, 100 specimens, small size, $5.00. 
100 specimens, large size, $10.00. These specimens are 
each accompanied by a label giving name, system of 
erystallization, chemical formula, and locality, and make 
a good working collection for a student. 
EXCELSIOR COLLECTION for high schools and colleges 
200 specimens, nicely mounted on wooden blocks, with 
beveled fronts for receiving labels. Price, packed 
$100.00. School Bulletin just out. 
Loose Crystals. 
Small packages of free crystals for crystallographic study 
may be sent for inspection by mail at small cost. Ap- 
proyal boxes of cabinet specimens by express or freight. 
ROY HOPPING, 
MINERAL DEALER, 
5 and 7 Dey Street, NEW YORK. 
Horsford’s Acid Phosphate. 
Overworked men and women, the 
nervous, weak and debilitated, will find 
in the Acid Phosphate a most agree- 
able, grateful and harmless stimulant, 
giving renewed strength and vigor to 
the entire system. 
Dr. Edwin F. Vose, Portland, Me., says: 
‘¢T have used it in my own case when suffering 
from nervous exhaustion, with gratifying re- 
sults. I have prescribed it for many of the 
various forms of nervous debility, and it has 
never failed to do good.” 
Descriptive pamphlet free on application to 
Rumford Chemical Works, Providence, R. I. 
Beware of Substitutes and Imitations. 
For sale by all Druggists. 
NEW CATALOGUE. 
We have recently issued a new edition, revised and en- 
larged to 64 pages, of our catalogue of 
Books on Chemistry, Chemical 
Technology and Physics. 
It is arranged by subjects, and includes all the standard 
books in Chemical and Physical Science, as well as the re- 
cent literature up to date. 
A copy of this Catalogue will be sent free by mail to any 
address. 
D. Van Nostrand Company, 
Publishers and Importers of Scientific Books, 
23 Murray St. and 27 Warren St., New York. 
CONSTIPATION 
IN ADULTS AND CHILDREN. With special reference to Ha- 
_.4 bitual Constipation and its most successful Treatment by 
the Mechanical Methods. 
By HENRY ILLOWAY, M.D., 
Formerly Professor of the Diseases of Children, Cincinnati 
College of Medicine and Surgery ; formerly visiting phy- 
sician to the Jewish Hospital, Cincinnati, etc.; Member 
of the Medical Society of the County of New York, of the 
New York County Medical Association, ete. 
With many Plates and Illustrations. 
8vo. Cloth. Price, $4.00 net. 
PUBLISHED BY 
THE MACMILLAN COMPANY, 
66 Fifth Avenue, New York. 
SPECIAL NOTICE. 
Position desired in Engineering Offices, with 
view to advancement. Details, upon commu= 
nication. 
C. H. D., care of Science, 
66 FIFTH AVE., NEW YORK. 
HOUGH’S “AMERICAN WOODS” 
A publication illustrated by actwal specimens. 
WOODS FOR THE STEREOPTICON 
Enabling you to show upon the screen characteristic 
structures projected from nature itself. 
WOODS FOR THE MICROSCOPE 
Sections 1-1200 in. thick showing three distinct views of 
grain under each cover glass. 
WOOD SPECIMENS FOR CLASS USE 
Nothing equals these for use in the class-room. 
VIEWS OF TYPICAL TREES 
From Nature, photographs and stereopticon views. 
WOODEN CROSS-SECTION CARDS 
Perfectly adapted to printing (with type or steel plate), 
painting, India ink work, etc. 
If you are interested in wood or trees in any way send for 
our circulars and sample specimens. 
Address R. B. HOUGH, Lowville, N. Y. 
