412 



SCIENCE 



[N. S. Vol. XLV. No. 1165 



THE AMERICAN ASSOCIATION FOR 



THE ADVANCEMENT OF 



SCIENCE 



SECTION D— MECHANICAL SCIENCE AND 

 ENGINEERING. II 

 Hecent Developments in Details of Construction of 

 BricJc Pavements on Green Concrete Foundation 

 and Sand-Cement Super foundation: William C. 

 Perkins. 



Discussion of new methods of constructing brick 

 pavements. Two methods of construction: (1) 

 The laying of the brick directly on the green con- 

 crete, commonly called "the monolithic construc- 

 tion." (2) The laying of the brick on a super- 

 foundation of cement-sand commonly called ' ' the 

 semi-monolithic construction. ' ' 



Advent of a brick 3 inches in depth due to the 

 new methods of construction and discussion of the 

 advantages of a 3-inch brick. 



Discussion of the details of construction of the 

 monolithic type. 



Discussion of the details of construction of the 

 semi-monolithic type. 



(Slides will be used showing the different steps 

 of construction.) 



The Causes of CracJcs in Cement-Concrete Pave- 

 ments: A. T. GOLLDBECK. 



This paper gives data on the relative effect of 

 moisture and temperature in causing cracking of 

 concrete pavements. The results of laboratory 

 tests on the effect of moisture on concrete are 

 given as well as the results of field measurements 

 on concrete roads. Likewise some results of fric- 

 tion tests of concrete slabs on various sub-bases 

 are presented and applied in analyzing the effect 

 of expansion and contraction in causing cracks. 

 Finally, the effect of lack of uniform support by 

 the sub-base in causing longitudinal cracks is 

 pointed out. 

 A Condition Survey of Concrete Boads in the United 



States: A. N. Johnson. 

 The Necessity for Adequate Methods of Water- 

 proofing in Eoad Construction : B. A. Meter and 

 C. J. Morrison. 



A wheel and a road may be considered as two 

 elements of a machine and the ideal requisites for 

 each determined to be: 



1. Perfectly hard and perfectly round wheel. 



2. Perfectly hard and level road. 



The ideal road can not be maintained, but can 

 be approached by constructing a moderately hard 

 road which resists wear and disintegration. 



In order to fulfil their requirements roads must 

 be water-proof so as to protect them- from the flow- 



ing, undermining and penetration of water. Prin- 

 ciples of waterproofing are simple, but are ne- 

 glected. Illustrated by drawings and pictures. 



Eoads are constructed under five general con- 

 ditions : 



1. On level ground. 



2. On inclined ground 



3. In cuts. 



4. On embankments. 



5. On side of slopes. 



Each condition requires a different method of 

 waterproofing, and waterproofing is dependent 

 upon: 



1. Location of drains. 



2. Construction of road. 



3. Treatment of surface. 

 Comparative costs of construction and mainte- 

 nance show that at the end of five years the total 

 cost of a non-waterproof road and that of a semi- 

 water-proof road are about equal, but that the 

 former is practically useless while the latter shows 

 little deterioration. 



Similar comparisons for waterproof roads are not 

 yet available. 



Columbia Miver Highway: George C. Warren. 



The fourth session was held in the morning, Fri- 

 day, December 29, in the engineering building, Co- 

 lumbia University, Vice-president, Dr. Henry M. 

 Howe in the chair, with an attendance of about 45. 



The program of the session, which was devoted 

 to general engineering, was as follows: 

 Modern Methods of Precise Leveling in the Coast 



and Geodetic Survey: William Bowie. 



Development of the Systematic Sydrographio Sur- 

 vey : N. H. Heck. 



Difference in popular and scientific attitude 

 toward the two branches of the Coast and Geodetic 

 Survey work. 



Lack of appreciation of hydrographic problems 

 with reasons. Conservatism of sea reacts on sur- 

 vey methods. Instances. 



Numerous sources of possible error to be elimi- 

 nated. Pressure of commercial needs interferes 

 with experimental work. 



Closer attention to care in location. Elimina- 

 tion of errors due to currents in certain offshore 

 areas. Startling results of a simple change. Im- 

 provements in depth measurements. Possible 

 errors in a long-established method. 



Failure of vertical method of developing aU bot- 

 tom contours introduced need for wire drag 

 method. Mathematical definition. Aims and 

 classification. 



