36 
curves, which is usually more abrupt on leaving than on 
entering a curve; the deeper impression due to standing, at 
stops in soft soil, the impression being more pronounced at 
its rear side; the Y where a machine backs out from a 
roadside stop. Even if no one sign is conclusive, the sum 
of thos3 gathered by following the track closely for some 
distance will in most cases lead to a sure conclusion. 
Excessive speed will almost always be disclosed by 
wind-whirl disturbances of the track, the distance of 
side throw of sand, mud, or water, side lurch on rough 
road, and the length of wheel jump in passing over ob¬ 
stacles. The size of car is approximately indicated by 
the width of tire tread, although this is affected by the 
amount of load, as well as by the air pressure in the tires. 
When the load is heavy, there is a higher piling up of the 
dust ridge which is left in the center of the # wheel track 
by the suction and thrust of traction on pneumatic tires. 
Proficiency in tracking .—Whether of men, animals, or 
autos, proficiency in tracking can be gained only by actual 
practice, and plenty of it. While trackers can not be 
made from books, one tracker can often tell another new 
kinks, and all can learn more by study. Let every man 
keep his eyes open and send in for the benefit of all the 
new things which he learns or clues familiar to him but 
not mentioned here. 
Moreover, many who know are not able to explain 
clearly how they know, and the discussion in these in¬ 
structions will help them in such explanation. The 
importance of this must not be overlooked; in court this 
question will surely be raised, and the opposing attorney 
will discredit testimony that does not answer it. “You 
must not only know that you know, but also know how 
you know.” 
Record of tracks .— 1 The original track, or a cast or replica 
of it, is the most convincing evidence. 
The original footprint can often be solidified sufficiently 
by means of water glass to be dug out and preserved. 
This is specially useful in sand or sandy soils. If the soil 
containing the print is firm enough not to be displaced by 
it, the water glass can be poured directly into the print. 
