•O 



SCIENCE 



New Seeies. 

 Vol. IX. No. 224. 



TfwmAv At>t?tt 14- ISQQ single copies, is cts 



TKIUAY, ii-FKiL, L% iOyy. Annual Subsceiptioi 



Annual Subsceiption, $5.00 



Queen Self-Regulating X-Ray Tube 



Less than two years have passed since the Queen Self-Regulating X-Ray Tube was announced. It won imme- 

 diate recognition as the most important improvement made in high vacuum tubes for the purpose of generating 

 X-Rays. It gives the operator power to control and regulate the vacuum and he can thereby vary the penetrating 

 power and other qualities of the X-Rays to suit the wortc in hand. It has, therefore, become almost universally 

 recognized as a necessity to radiographers who wish to do rapid and reliable work, and as an absolute essential to 

 those who would be in position to render to the surgeon all the aid their science is capable of furnishing. In 

 autograph letters, Professor Roentgen and Lord Kelvin have paid tribute to its "ingenuity" and "most satisfac- 

 tory" working qualities. We have just issued a .36-page pamphlet completely desci-ibing it and giving detailed 

 instructions for its use, which will be sent free to inquirers. 



QUEEN & CO., INC. 



Optical, Electrical and Scientific Instrument Works 



1010 Chestnut St., Philadelphia 



NEW YORK BRANCH : 



59 Fifth Avenue 



