D7 
seven from north to south. In general the soundings were along land 
survey lines 80 rods apart. The distance between soundings along these 
lines was fifteen oar strokes. In sounding they used a block of iron for 
a sinker and a fine wire for a line. The wire was wound upon a wheel 
of known circumference. and measurements were calculated from the 
number of turns made in winding up the line. While sounding Professor 
Drybread did the rowing, Mr. Smith made the soundings and Mr. Denny 
kept the record. Professor Drybread made a sketch map and platted in 
the work from day to day, making profiles of the dines, which frequently 
suggested mistakes, so that several lines were worked over a second 
time. In all, the party made nearly five hundred soundings. The party 
worked carefully, and the sounding was done as accurately as possible 
under the circumstances. <A study of their work reveals some of the dif- 
ficulties which hinder accuracy in such lines of work. Knowing: the 
length of the line and the number of stations, it was easy to calculate the 
average distance between stations. This distance varied on the different 
lines from 190 feet to 300 feet and Professor Drybread’s oar strokes varied 
from 13 to 20 feet in length. This was doubtless mainly due to rough 
water and wind, perhaps partly to the length of some of the lines. On 
the line running north across Long Point the distance between sta- 
tions on the south was 267 feet where the water was quiet, while 
north of the point in rough water the average distance was 233 feet. The 
longest strokes were on the north line of section 34, where the water was 
quiet and the line short. In rough water it was difficult to hold the boat 
in position while the sounding was made. If the strokes were uniform 
for the whole length of the line there would be no difficulty, but the irreg- 
ularity might reach each extreme of variation along any one of the longer 
lines, involving variations of at least 50 feet from the average. We found 
places in Lake Maxinkuckee where a distance of 50 feet meant a differ- 
ence of 25 or 30 feet in depth. Another source of error was in the diffi- 
culty of following the lines. The lines were so long that it was not 
possible to see the flags or signals, and it is not easy to follow a line 
closely when rowing by a compass, especially when a stop and start must 
be made every 250 feet. This method of sounding, of course, does not 
aim at the accuracy attained by the coast survey, with their refined in- 
struments and methods, but it should be accurate at least within 50 
feet in distance. To insure this degree of accuracy the work must be 
done on quiet water and along short lines, so that the man at the oars 
