364 BELL SYSTEM TECHNICAL JOURNAL 



lated from the rate of decrease of ionization after the passage of a 

 meteor, to be less than 0.2 x 10~^ cubic centimeters per second. 



Small Sapling Method of Evaluating Wood Preservatives.^ R. E. 

 Waterman and R. R. Williams. Permanence and toxicity are 

 probably the most necessary characteristics of a wood preservative. 

 Ease of injection, freedom from corrosive properties, cleanliness, cost, 

 and the like are all important, but no material can be considered unless 

 it displays a high degree of resistance to wood-destroying fungi and 

 unless this toxic potency persists when the treated wood is exposed to 

 the weather for long periods of time. The problem under discussion 

 is that of appraisal of wood preservatives for these two characteristics 

 within a reasonably short time. 



In order to expedite tests of the permanency of pole preservatives, 

 use is made of groups of small pine saplings treated with the preserva- 

 tive in question and set in the ground as miniature telephone poles. 

 In these specimens weathering is relatively rapid on account of the 

 large ratio of surface to volume, and poorly preserved material begins 

 to decay in one or two years. Analyses and toxicity tests as well as 

 observations of decay are made periodically. Seven years' experience 

 indicates that the comparative preservative values of various salts, 

 creosotes, oils, etc., may be estimated relatively cheaply, quickly, 

 and with considerable reliability by this method. 



A High Speed Level Recorder for Acoustic Measurements }^ ^ E. C. 

 Wente, E. H. Bedell and K. D. Swartzel, Jr. Two quite accurate 

 means for recording rapid variations in sound intensity in a form 

 suitable for visual inspection have been available for a number of 

 years. One of these is the phonodeik, or one of its variants, and the 

 other is a combination of a microphone and an oscillograph. When 

 properly designed these devices record the actual wave form of the 

 sound. However, for many acoustic measurements, a knowledge of 

 the wave form is of secondary interest, whereas it is important that 

 one should be able to record rapidly varying mean intensities over a 

 wide range of values. From a record of the wave form it is not easy 

 to determine the intensity with any degree of accuracy for a range 

 greater than 20 or 30 db, but in some types of acoustic measurements 

 it is highly desirable that the record cover a range of at least 60 db. 

 Recently several types of instruments have been built which record, 

 on a logarithmic scale, the mean power of the electrical input. These 

 instruments, like that described here, may be used to plot the intensity 



^ Indus, and Engg. Chem. {Analytical Edition), November 15, 1934. 

 1° Jour. Acous. Soc. Amer., January, 1935. 



