Mabch 10, 1911] 



SCIENCE 



395 



building in the United States, noting that from 

 the time of the advent of railroad construction, 

 little or no attention was given by engineers to 

 road work until about 1890, when some of the 

 eastern states took up the question of road im- 

 provement from state-wide view points, since 

 which time large sums of money have been appro- 

 priated by different states for the systematic 

 study and construction of roads; that this work 

 is now demanding the service of trained men and 

 the people generally are realizing the necessity of 

 such service. 



In presenting the paper, the writer illustrated 

 with lantern slides some of the conditions found 

 in highway work in Illinois and the methods of 

 the road and bridge construction undertaken by 

 the Illinois Highway Commission which would 

 be representative of the conditions and methods 

 applicable to a wide area of the Mississippi Val- 

 ley region. 



Methods of Taking Traffic Census on Highways: 

 A. H. Blanchabd and I. W. Pattekson, Provi- 

 dence, R. I. 



The value of statistics relative to traffic on 

 highways, taken previous to their construction, 

 is generally admitted; but the methods to be 

 employed in the securing of such statistics have 

 not been discussed in the technical press except 

 relative to the classification of traffic. 



In view of the fact of their close relation to 

 the wear of a road surface, the following ele- 

 ments of classification should be noted: differen- 

 tiation between horse-drawn and motor-car traffic, 

 distinction between pleasure and commercial 

 traflie, subdivision of commercial traffic into 

 loaded and unloaded vehicles, weight per linear 

 inch of tire of commercial traffic, number of 

 horses drawing vehicle, weight and speed of motor 

 cars and abnormal local traffic of e.xtraordinary 

 character. Numerous highway supervisory bodies 

 have drawn up forms which include the above 

 important items more or less completely. 



The methods of securing traffic data are of 

 extreme importance. The methods where two 

 extremes of time (one year and one month) are 

 available for traffic census are discussed. The 

 following three methods applicable in both cases 

 are considered : ( 1 ) observations upon single 

 days at regular intervals; (2) observations 

 through a period of several consecutive days at 

 intervals; (3) observations covering a period of 

 three days, including Saturday and Sunday, at 

 intervals. The last-named method appears from 

 the standpoint of economy of labor, probable clem- 

 ency of weather (weather conditions at Provi- 



dence, E. I., considered in each case for a period 

 of five years), and results obtained to be the 

 most practical method for general use. 



The Present Status of the Relationship betioeen 

 Laboratory Tests a/nd the Use of Road Ma- 

 terials: W. W. Cbosby, Baltimore, Md. 

 The science underlying the art of roadmaking 

 is obtaining recognition. For its development, 

 laboratory tests and records of experience are 

 necessary. Some such have been available in the 

 past, but these are, from their incompleteness, 

 unsatisfactory now, especially as regards new 

 materials and altered conditions of traffic. By 

 reference to the records and use of such tests as 

 those for the resistance to abrasion of stone and 

 the cementing qualities of the stone powder, is 

 shown the value of such tests, and, at the same 

 time, the incompleteness of the present knowledge. 

 More complete information is stated to be de- 

 sirable as well as information along other lines, 

 such for instance as the strength of stone under 

 compression. 



The changes in traffic conditions, and the new 

 records of the experience with both old and new 

 materials under the changed conditions are re- 

 ferred to with some suggestions as to what defi- 

 nite information may be desirable. 



The statement is made that records from ex- 

 perience are needed, and not conclusions from 

 assumed theories alone. Also that the author 

 believes it may be possible eventually to reduce 

 many of the problems of highway engineering to a 

 mathematical solution. The beginning of the 

 work of collecting information, and the desira- 

 bility of cooperation are mentioned. 



Dr. Octave Chanute and his Work in Engineering 

 and Aeronautics: James Means, Boston, Mass. 

 An appreciative review of the achievements of 



Dr. Chanute. (Published in full in Science.) 



jfermanent Winds, their Causes and Directions: 

 W. J. Hdmpheeys, Washington, D. C. 

 The temperature difference between tropical 

 regions and those of higher latitudes establishes 

 a barometric gradient from the warmer to the 

 colder parts of the earth. The resulting flow of 

 the air together with the rotation of the earth 

 causes the air of higher latitudes to flow from 

 west to east, and that of the equatorial regions 

 from east to west. The opposing centrifugal 

 forces thus set up are the cause of belts of high 

 pressure at latitudes 30° to 35° both north and 

 south. 



These belts of high pressure are underrun at 

 five places, two in the Pacific Ocean, two in the 



