678 



SCIENCE 



[N. S. Vol. XXIX. No. 747 



ing and Camp Outfits," by A. fci. Hitchcock, \. 

 Bailey, H. S. Barber, W. H. Osgood, J. W. Gidley 

 and E. A. Preble. Articles of camp equipment 

 were exhibited, methods of carrying packs dem- 

 onstrated, and many lantern slides shown. 



M. 0. Mabsh, 

 Recording Secretary 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 663d meeting was held March 27, 1909, 

 Vice-president Wead in the chair. Two papers 

 were read. 

 The Present Status of Wireless Telegraphy and 



Telephony : Dr. L. W. Austin, of the Bureau 



of Standards. 



Two years ago there were four principal prac- 

 tical problems before the workers in radio- 

 telegraphy: 



1. Doing away with the irregularities of the at- 

 mospheric absorption of the signals which caused 

 waves of the same intensity to be at one time 

 detected at a distance of 1,000 miles, at another 

 not over 100. 



2. The elimination of the disturbances in the 

 receiving station due to atmospheric discharges 

 which frequently made the reception of signals 

 entirely impossible. 



3. The production of directed signals capable ol 

 commercial use. 



4. The production of electrical oscillations suit- 

 able for wireless telephony. 



The first of these problems has been successfully 

 attacked by Professor Fessenden, who has shown 

 that by using a wave-length of approximately 

 4,000 meters the absorption is much reduced and 

 becomes practically constant under all conditions 

 both by day and night. 



The second problem is still not satisfactorily 

 solved, although the conditions are much improved 

 by sharper tuning of the receiving circuits and 

 especially by the use of a loose coupling of the 

 receiver. 



In regard to the third problem, a certain amount 

 of success has attended the experiments of Mar- 

 coni, who by using a bent antenna has succeeded 

 in giving direction to the electrical waves. Bellini 

 and Tossi in France have also obtained very satis- 

 factory results by the use of a kind of loop 

 antenna. 



In wireless telephony, continuous trains of oscil- 

 lations produced either by the arc or by means of 

 high-frequency dynamos have been so far improved 

 that the range of working has been increased from 

 about 10 miles to over 200. 



A Calorimeter for the Determination of the Spe- 



cifio Beat of Liquids: Mr. H. C. Dickinson, 



of the Bureau of Standards. 



A Dewar flask of the ordinary spherical form, 

 of five liters' capacity, has been adapted for use 

 directly as a calorimeter for measuring the spe- 

 cific heat of liquids. Tne particular problem 

 attacked has been the measurement of the specific 

 neat of calcium chloride solutions at low tempera- 

 tures. For this purpose the flask is immersed in 

 a mixture of ice and water and filled with the 

 solution to be tested, cooled to the lowest tempera- 

 ture its concentration will permit. 



The method consists in accurate measurements 

 of the temperature of the weighed contents of the 

 flask, alternating with short periods during which 

 energy is supplied electrically to raise the tem- 

 perature of the liquid. The temperature is raised 

 by steps of about 5° C. and the energy supplied, 

 and the corresponding rises of temperature are 

 measured for each 5° interval. Such a series of 

 observations with a single sample of solution, occu- 

 pying about one and a half hours, gives a specific 

 heat for intervals of 5°, between — 30° C. and 

 + 20° C. 



The water equivalent and radiation constant for 

 the calorimeter were determined with great care 

 by a separate series of experiments, using pure 

 water. The water equivalent of the calorimeter, 

 stirrer, thermometer, etc., is only about 2 per cent, 

 of the total water equivalent of the solution used. 



The total correction for radiation with a tem- 

 perature difference of 30°, amounts to only about 

 two per cent, of the energy supplied. 



The energy, supplied electrically, is measured to 

 about 2 parts in 10,000 by means of a potentiom- 

 eter in connection with a standard 0.1-ohm shunt 

 and a volt bo.x. 



Temperature diff'erences are measured by means 

 of a resistance thermometer having a sensibility 

 01 about 0°.0005 C. 



The time intervals necessary in computing the 

 total energy are measured by means of a tape 

 chronograph to about 0.02 second. 



The following table gives the values found for 

 the specific heat of solutions of chemically pure 

 calcium chloride and water of different densities, 

 wliere t is the temperature in degrees 0. : 

 Density Specific Heat Temperature 



1.07 0.869 + 0.00057* (—5° to +15°) 



1.14 0.773 + 0.00064 t {— 10° to + 20°) 



1.20 0.710 + 0.00064 « (—20° to +20°) 



1.26 0.662 + 0.00064 t ( — 25° to + 20° ) 



R. L. Fabis, 

 Seereiary 



