SCIENCE—ADVERTISEMENTS 
Handy 
Resistance Units 
These are furnished in single value blocks, 
ranging from 0.1 ohm to 10,000 ohms. Blocks 
for all values are uniform in size, and can 
readily be arranged in groups to build up any 
desired resistance. Adjustment is made to 
within 1/20 of one per cent. 
We have just issued a new Circular (No. 10), 
describing and listing these units. Write 
for it. 
Circular No. ro also describes a new two-value 
Unit, especially designed for teaching purposes, 
to check up students on reststance measurements. 
PYROLECTRIC INSTRUMENT Co. 
Pyrometric and E lectrical Preciston Instruments 
636 EAST STATE STREET TRENTON, N. J. 
E. F. Northrup, President and Technical Adviser 
Tycos 
Temperature Instruments 
Mercurial, Recording and 
Index Thermometers for 
all industrial and labor- 
atory applications. 
Electric Contact Ther- 
mometers. 
Temperature Pressure and 
Time Regulators. 
Mercury Column Vacuum 
Pressure and U Gauges. 
Base Metal,Rare Metal and 
Radiation Pyrometers. 
Fery Radiation Pyrom- 
eters. 
the trade- 
TY COs; eee 
an organization manu- 
facturing indicating,re- 
cording and controlling 
Temperature Instru- 
ments of the better type, 
giving utmost satisfac- 
tory service ; an organ- 
ization that serves its 
trade sincerely in all 
Hssromieiels 5 ° 
Hydrometi dealings. The convinc- 
ainesae ol ‘Testing Instru- | ing proof of high quality 
of product is its growth. 
Correspondence in- 
vited. We will do our 
best to give you the in- 
formation desired, and 
not subject you to a 
Aneroid Barometers 
Mercurial Barometers 
Recording Barometers 
Pocket Compasses 
Surveying Compasses 
Rain Gauges. 
noone tere: long and mechanical 
Thermographs. series of follow-up let- 
Hand Levels. ters. 
tae pele. 
inclinometers 
Sphyemomanometers. Taylor Instrument Co.’s 
Fever Thermometers. 
Urinary Glassware. 
Thermometers of all kinds 
for home and General Use. 
ROCHESTER, N. Y, 
There’s a Tycos and Taylor 
Thermometer for every purpose 
SCHOOL AND SOCIETY: 
A weekly journal covering the whole field of 
Education in relation to the problems of American 
democracy. Published every Saturday. 
Annual Subscription, $3.00 
Single Numbers, 10 cents 
THE SCIENTIFIC MONTHLY 
An illustrated magazine, devoted to the diffu- 
sion of science, publishing articles by leading au- 
thorities in all departments of pure and applied 
science, including the applications of science to edu- 
cation and society. 
Annual Subscription, $3.00 
Single Numbers, 30 cents 
THE AMERICAN: NATURALIST 
A monthly journal, established in 1867, devoted 
to the biological sciences with special reference to 
the factors of organic evolution. 
Annual Subscription, $4.00 
Single Numbers, 40 cents 
THE SCIENCE PRESS 
Garrison, N. Y. 
Lancaster, Pa. 
Cooking Class at the 
South Dakota State College 
are using gas made by 
The “Detroit” _ 
Combination Gas Machine 
for supplying gas in Departments of 
Domestic Science 
Chemistry and Physics 
(Over 30,000 in daily use) 
Laboratory work can be done better, 
quicker and cheaper by using this gas. 
Ask for descriptive catalog 4nd names 
of users in your vicinity. 
Detroit Heating & Lighting Co. 
612 Wight St. Detroit, Mich. 
