POLAR EXPLORATION 



4730 



POLARIZATION OF LIGHT 



Island, a dreadful, glacier-covered stretch of 

 land, exposed to the fiercest storms and without 

 an inhabitant. With a heroism unsurpassed in 

 the annals of polar research, Shackleton and 

 five volunteers set out on a relief expedition, 

 navigating the wild sea in an open boat twenty- 

 two feet in length. On the tenth of May they 

 disembarked safely on the west shore of South 

 Georgia, made an overland trip across ice- 

 covered mountains, and on May 31 reached a 

 Norwegian whaling station. Three times a res- 

 cue ship set sail to relieve the men on Elephant 

 Island, and each effort failed. The undaunted 

 Shackleton, however, refused to be defeated, 

 and finally, on August 30, 1916, in the Chilean 

 steam yacht Yelcho, reached the marooned 

 travelers, all of whom he found alive. They 

 had conserved their food supplies by killing 

 penguin, shellfish and seal. 



Meanwhile a supporting expedition under 

 Captain E. Mackintosh had sailed in the Au- 

 rora. The purpose of this company was to lay 

 supply depots on Ross Barrier (see map, page 

 276) for the use of Shackleton's party, which 

 had expected to reach Cape Evans on June 1, 

 1915. Captain Mackintosh and several men 

 went ashore, while the rest of the party re- 

 mained on the Aurora, which was anchored to 

 the ground ice at Cape Evans. On May 6, 1915, 

 the Aurora was loosened from its moorings by 

 a terrible blizzard and was swept out to sea. 

 After drifting in the ice for many weeks the 

 reached Australia. The men left on 



Roes Barrier continued their work of laying 

 supply depots. This they accomplished with 

 almost superhuman courage, for they were be- 

 set by furious blizzards. Moreover, scurvy at- 

 tacked the party and rendered some of them 

 helpless, Captain Mackintosh and two of the 

 men dying from the effects of the hardships. In 

 December, 1916, Shackleton started on a relief 

 expedition from New Zealand in the Aurora. 

 He arrived at Cape Evans on January 10, 1917, 

 rescued the survivors and arrived at Welling- 

 ton, New Zealand, on the fifth of February. 

 Thus ended one of the most thrilling chapters 

 in the history of polar explorations. B.M.W. 



Consult Scott's Scott's Last Expedition; Amund- 

 sen's The South Pole: An Account of the Nor- 

 wegian Antarctic Expedition in the Fram 1910- 

 1912; Shackleton's Heart of the Antarctic; Peary's 

 Nearest the Pole; Cook's My Attainment of the 

 Pole; Greely's Handbook of Polar Discoveries 

 .(5th edition). 



Related Subjects. The following articles In 

 these volumes contain much that will be of inter- 

 est in connection with the subject of polar ex- 

 ploration : 



Abruzzi, Duke of the 

 Amundsen, Roald 

 Antarctic Lands and 



Seas 



Arctic Lands and Seas 

 Cabot, John and Sebas- 

 tian 



Challenger Expedition 

 Cook, Frederick A. 

 Cook, James 

 Earth 



Franklin, Sir John 

 Frobisher, Sir Martin 



Hudson, Henry 

 K;uu>. Klisha Kent 

 Nansen, Fridtjof 

 Nordenskiold, Nils A. E. 

 Northwest Passage 

 Parry, Sir William E. 

 Peary, Robert E. 

 Pole 



Ross, Sir James Clark 

 Scott, Robert Falcon 

 Shackleton, Sir Ernest H. 

 Stefansson, Vilhjalmur 



POLARISCOPE, an instrument for produc- 

 ing and testing polarized light. Polarization of 

 light (which see) is a process by which vibra- 

 tions of light rays are made to take a single 

 direction. The simplest polariscope is a crystal 



A POLARISCOPE 



of Iceland spar or a crystal of tourmaline. The 

 polariscope may be made by mounting crystals 

 of these minerals so that they can be inserted 

 in the tube of a microscope in place of the eye- 

 piece, or a separate apparatus may be used. 

 The upper tube can be turned so that the axes 

 of the crystals are placed at right angles when 

 the polarizing effect on the object viewed is 

 seen. This instrument is sometimes used for 

 testing the quality of sugar (see last sentence, 

 article POLARIZATION OF LIGHT). 



POLARIZA'TION OF LIGHT. Were it pos- 

 sible to look at the end of a magnified ray of 

 light it would be seen to resemble the end of 

 a sawed-off log or branch after it had become 

 dry. That is, there would be innumerable lines 

 radiating from the center of the ray, like the 

 little cracks that radiate from the center of the 

 end of the branch (Fig. 1). Scientists know 

 this supposition to be well founded, because 

 they have proved beyond doubt that the ether 

 waves which propagate light vibrate at right 

 angles to the direction in which the ray travels. 

 White light is composed of all the colors of 

 the spectrum (see LIGHT;, each color being due 

 to different wave lengths. All these waves pass 



