SCIENCE— ADVERTISEMENTS 



JAGABI DIAL PATTERN 



RESISTANCE BOXES 



and 



WHEATSTONE BRIDGES 



For use in Research. Industrial and Edu- 

 cational Laboratories these instruments are 

 recommended — as combining first class ma- 

 terials, excellent workmanship and moderate 

 prices. 



No plugs are used; and the dials are ar- 

 ranged to be "direct-reading," a matter of 

 quite some importance. 



The boxes are dust-proof, with hard rub- 

 ber tops. The coils are of manganin wire, 

 wound bi-filar on metal spools and are cali- 

 brated within i/io of i per cent. 



In the Resistance Boxes each dial controls 

 9 coils of like value — which plan eliminates 

 "kicks" in a telephone receiver or galvano- 

 meter when the switch is being rotated. 



The Wheatstone Bridge includes four sets 

 of coils, 9 X (i+io-l-ioo+iooo ohms), and 

 the bridge coils have a dial control which 

 multiplies by .001, .01, o.l, i, 10, 100 or 1000 

 — thus simplifying construction and opera- 

 tion as compared with two separate "arms." 



Write for illustrated descriptive 

 Bulletin S-iooo. 



JAMES G. BIDDLE 



SCIENTIFIC INSTRUMENTS 

 1211-13 Arch St., Philadelphia 



CAMBRIDGE 



BOY'S RADIOMICROMETER 



An extremely sensitive instmment 

 for the measurement of radiant heat. 



The suspended system consists of a 

 single loop of silver wire having 

 at its lower extremity a sensitive 

 thermo-couple. The thermojunction 

 carries a receiving plate of blackened 

 copper foil. The radiation received 

 on this plate raises the temperature 

 of the thermo-junction and causes a 

 small current to flow in the silver 

 loop, which is consequently deflected. 



Send for list No. 100 



Also manufacturers of all types of 

 Physical and Electrical Instruments. 



(Tiaoeandrai 



INSTRUMENT G9 «f AMER1CA(/^| 



Works MPU/ \/r\0]X OfficeaShowroom 



OssiNwo-oN-HuDSON INlVV YvyhC iX GrandCemtpalTepminai. 



