182 BAILEY WILLIS — GKAPHIC FIELD KOTES. 



Measurement with a wheel is an old method, improved within the last few 

 years to meet the demand of the topographic division of the United States 

 Geological Survey for an efficient means of traverse work. Mr. Henry 

 Gannett says of it : 



" As nearly all traversing is done along roads, distances are measured in this work 

 mainly by counting the revolutions of a wheel — usually one of the wheels of a buggy 

 or buckboard. Various forms of odometer for automatic counting have been in use. 

 The old pendulum odometer was first tried and unqualifiedly condemned. The form 

 now in general use is that devised by Mr. E. M. Douglas, of this Survey. For work- 

 ing this a cam is placed on the inside of the hub, which, by raising a straight steel 

 spring, carries the index forward one division for each revolution of the wheel. The 

 odometer registers to ten thousand. This form is the most trustworthy that has yet 

 been devised, but is not altogether satisfactory, and the majority of traverse men pre- 

 fer to count the revolutions of a wheel directl3^ The arrangement by which a bell 

 is rung at each revolution is a ver\^ common and effective device. From an extended 

 experience covering many thousands of miles of measurements it has been demonstrated 

 that as a working method of measuring distances the wheel is greatly superior upon 

 roads to the stadia. Moreover, it is nearly if not quite twice as rapid as the stadia 

 method."'^ 



The attachment of the Douglas odometer to the wheel varies with the 

 ingenuity of individual users: it may be placed on either axle, when its con- 

 nection with the wheel is then most direct ; or it may be placed beside the 

 seat of the vehicle and connected with the wheel by wires working a system 

 of levers. The latter arrangement requires nice adjustment but raises the 

 odometer out of the reach of mud, places it within convenient observation 

 and enables the observer to judge the regularity of its register by the click 

 of the ratchet. 



Pacing, as a means of measuring short spaces, we are all familiar 

 with ; but pacing mile after mile, day after day, for continuous record 

 is not a common practice. It was only after experience had demonstrated 

 both the necessity and practicability of pacing that I gave the method 

 practical consideration. Where the wheel can be driven it has the advan- 

 tage ; but where the Avheel must stop, the pace becomes a convenient 

 and indeed indispensable unit of measure, w^hich never fails one who has 

 practiced it. It may be confidently stated from repeated experiences that 

 there is no condition of surface, of slope, or of obstruction, over or through 

 which a man cannot pace, with a reasonable approximation to the true dis- 

 tances, provided the ends of the meander line are so tied to some control 

 that the scale of the meander plat can be independently determined. Sys- 

 tematic pacing for geologic record was first used by the Canadian 

 Survey and in the United States by Brooks and Pumpelly in the 

 Lake Superior region. The United States Land Survey there divided 

 the country into square miles and within these north or south straight 



* Unpublished MSS. 



