12 
IOWA ACADEMY OF SCIENCE Voi,. XXIX, 1922 
Topics in General Analysis. E. W. Chittenden 
The Place of the Equation in a Scheme of Education. C. W. Wester 
Pre-symmetric Determinants whose Elements are Finite Sums. E. R. 
Smith 
On the Meaning of the Classification of Statistical Series by Means 
of the Lexis Ratio. H. L. Rietz 
Definitions of Imaginary and Complex Numbers. E. S. Allen...... 
An Extension of the Figurate Numbers. J. F. Reilly 
Physics 
A Redetermination of the Principal Reflecting Powers of Isolated 
Selenium Crystals. L. P. Sieg 131 
Solubility and Polarity. Wm. Kunerth. 135 
A Comparison of Intensities Required Under Direct and Under In- 
direct Lighting Systems. Wm. Kunerth..... 141 
The Path of a Rigid Electron Which Moves in a Magnetic Field of 
Constant Strength Rotating With Constant Angular Velocity. E. 
O. Hulburt 147 
Phenomena in Gases Excited by Radio Frequency Currents. E. O. 
Hulburt ... 147 
The Broadening of the Balmer Lines of Hydrogen With Pressure. 
E. O. Hulburt .. 148 
Nodal Distances in Acoustics. G. W. Stewart..... 149 
A Variable Single Band Acoustic Filter. G. W. Stewart 150 
A New Form of Telephone Receiver and Transmitter. C. W. Hewlett 151 
Efficiencies of Automobile Headlight Lenses by Box Photometer Meth- 
od. D. M. Smith 
The Scattering of X-Rays by Light Elements. C. W. Hewlett 151 
The Hall Effect and Specific Resistance of Evaporated Films of Silver, 
Copper and Iron. J. C. Steinberg ...... 153 
The Attenuation Factor in Acoustic Wave Filters. H. B. Peacock. . . . 155 
Coefficients of Diffusion of Salt Vapors in the Bunsen Flame. George 
E. Davis 155 
Zoology 
Iowa Microlepidoptera. A. W. Lindsey. 157 
Brood A of the White Grub Extends its Range in Iowa. H. E. Jaques 163 
A Study of the Eggs of the White-Marked Tussock Moth. Miss 
Susannah Poulter and H. E. Jaques 165 
A Scribofacilograpfi for Labelling Kymographic Tracings. T. L. Pat- 
terson 169 
Effects of Stretch on Smooth Muscle Responses. B. M. Harrison 173 
Observations on the Habits of a Tarantula in Captivity. Albert 
Hartzell 187 
Some Recently Published Errors Respecting the Cranial Nerves of the 
Dogfish. H. W. Norris ........ 
Cranial Nerve Components in Amia, Lepidosteus, Polyodon and 
Scaphirhynchus. H. W. Norris 191 
Some Hereditary Pathogens. W. E. Sanders 
