b2S Professor Hoivard T. Barnes [May 31, 



with the salt water, but leave it practically unatl'ected. Pettersson 

 believes that this circulation has an important influence on the 

 currents in the sea. I have found that the sea becomes diluted by 

 this fresh water over a very wide area. The lower density of this 

 diluted layer prevents the normal vertical circulation in the sea, and 

 causes characteristic temperature effects.* 



Icebergs which have been left high and dry on the shore by the 

 tide show the action of the melting. Bergs which become top-heavy 

 and turn over also bear evidence to the underwater current producing 

 the melting. The form of the ice shows a deep furrow running all 

 around where the melting process has proceeded, and this is often 

 the cause of the rolling over of a berg to find equililjrium in some 

 other position. Icebergs are often in an exceedingly unstable state, 

 and the slightest increase in wind or sea disturbance causes them to 

 break up or turn over. This is one of the reasons why captains 

 always go as far away from them as possible. 



Signs of the Proximity of Ice. 



Since the earliest days efforts have been made to find some means 

 of detecting the presence of ice. To those who have had many years' 

 experience in navigating in the ice region the presence of ice is 

 made known by a number of effects. Before ice can be actually 

 seen there is a pecuhar whiteness observed around the berg on a dark 

 night, except in the case of dark bergs. This is called by mariners 

 the ice "blink." It is caused l)y the reflection of the scattered rays 

 of light from the sky from the white surface of the berg. Thus, it 

 is a contrast between the black absorbing water, which reflects none 

 of the light, and the ice, which scatters nearly all. A dark berg is 

 one casting a shadow towards the ship. When the light comes more 

 strongly from any particular part of the sky the iceberg often cannot 

 be seen in certain directions, while clearly visible by the ice blink in 

 others. This I beheve to be the reason why the officers on the 

 " Titanic " did not see the berg soon enough to stop. It is stated that 

 on a clear day on the horizon over the ice the sky will be much paler 

 or lighter in colour, and may be distinguished from that overhead. 



During foggy weather, ice can sometimes be made out on account 

 of its darker appearance. In this case it is a contrast effect again, 

 but this time it is the shadow of the berg against the white shadow- 

 less fog particles. 



Icebergs arc sometimes detected by the echo from the steam- 

 whistle or fog-horn. They are also frequently heard for many miles 

 by the noise they make in breaking up and falling to pieces. The 

 cracking of the ice or the falling of the pieces into the sea causes a 

 noise like thunder. 



The altsence of swell or waves is sometimes a sign of ice or land, 



* [Recent experiments have shown this dilution to be very small. — August 

 27, 1912. H. T. B.] 



