The Operation and Use of the Apparatus 



is stationary. When we are two miles apart, the reflection of 

 our blasts rings the bells, and the indicator shows a different 

 record to what we have seen before. The markings on the 

 paper strip are of considerable size and commence sharp and 

 abrupt, but the ending is not sharp or distinct. There is 

 a tailing out of spots made by the zigzag lines. The total 

 length of the echo is thus made longer than that pro- 

 duced by the primary blast. This shows that there is 

 some kind of a cloud about the object of a different density 

 from the surrounding air and that it is of considerable size. 

 Therefore, we draw a logical conclusion. The object is of 

 great size ; it is stationary, and it has something about it 

 that modifies the echo ; consequently, the record on the paper 

 strip resembles that obtained from both a large, solid object 

 and a cloud. Therefore, it must be a large iceberg surrounded 

 by cold air. We change our direction so as to pass it on 

 our port side at a distance of half a mile. Fortunately we 

 have barely passed when the fog lifts and discloses an 

 enormous iceberg surrounded by smaller pieces of ice that 

 have been broken off. The following day we pass many ships, 

 and with our apparatus we inform them of the size and 

 locality of the big iceberg. We are now well off the Banks, 

 but still in a locality where icebergs may be found, and in 

 the afternoon we come in sight of a group of these danger- 

 ous objects of all sizes. We give them a blast and the record 

 produced is peculiar. Instead of one spot of zigzag lines 

 on the paper strip, there are about half a dozen spots. Each 

 iceberg within range has made its own record, indicated 

 roughly its size and accurately its distance. Soon night is 

 on us again, accompanied by a slight mist that obliterates 

 D 33 



