47 



temperature of air, 38. Size of berg above water: Height, 200 feet; 

 length, 600 feet; shape, regular. 



Observations. — While stopped, with the berg dead ahead, echoes could be 

 heard at 1,500 yards. Steaming toward the berg at 10 knots, no echoes 

 were heard until the berg was at a range of 400 yards. Circling the berg 

 at a range of 1,000 yards, very good echoes were heard. Circling the 

 berg at a range of 1,500 yards, weak echoes were heard. While circling 

 the berg better results were noted with the berg bearing abeam or abaft 

 of the beam than with it bearing forward of the beam. Steaming directh- 

 away from the berg at a speed of 10 knots, weak echoes could be heard at a 

 maximum range of 2,500 yards occasionally. 

 (d) Conditions.— Latitude 44° 00' N., longitude 49° 30' W. Depth of water 

 39 fathoms. Character of bottom, fine-grained sand, shells, and smiall 

 gravel. Temperature of water, 37; t'emperature of air, 47. Size of berg 

 above water: Height, 30 feet; length, 65 feet; shape, remains of "dry 

 dock," being irregular ridges with apparently solid base. 



Observations. — Approached berg from 2,500 yards at various speeds. At 

 maximum speed received echoes when close aboard; at slow speed, mod- 

 erate intensity, echoes were heard at 500 yards. Circled berg at various 

 distances and speeds, received good echoes from about 15° off either bow 

 at distances up to 1,500 yards. Intermittent echoes were heard while 

 circling up to a distance of 2,200 yards. AVeak echoes were heard at 

 2,500 yards at times. The best intensity was heard with bergs abeam or 

 abaft the beam. 



ECHOES 



While off the coast of Nova Scotia the sound apparatus was tested 

 for echoes in sandy bottom and rocky bottom with good results but 

 with varying intensities. 



CONCLUSIONS 



(a) It was established that the equipment installed on the Tampa 

 affords an efficient means of determining depths. 



(h) It was established that echoes of oscillator signals were re- 

 flected from icebergs and could be heard under favorable circum- 

 stances. 



(c) That such echoes varied in intensity, depending upon the 

 depth of water, character and contour of the bottom, the relative 

 bearing of berg with reference to oscillator, the speed of vessel and 

 the nature, form, and size of the reflecting surface, and the location 

 of the oscillator. 



(d) That the range at which echoes could be heard varied with 

 the relative bearings of the berg with respect to the vessel, being at a 

 minimum with the berg bearing forward of the beam, and also that 

 this range decreased when the speed of the vessel was increased due 

 to the increased amount of local disturbing noises in the location of 

 sound maker. 



(e) That with, the iceberg dead ahead and the vessel steaming 

 at 12 knots no echoes could be heard above a range of 500 yards, 

 even in 39 fathoms of water, and that better results for al 



uj L I B R A R Y 



