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THE POPULAR SCIENCE MONTHLY. 



of water, no longer retarded by the atmos- 

 phere and descending as rain would be un- 

 able to obtain food, from inability to move 

 themselves by any ordinary method of loco- 

 motion, or, what would be equally serious, 

 having once started into motion, from being 

 unable to stop except when they came into 

 collision with other unhappy beings or mov- 

 ing bodies. Before long they, with all heavier 

 substances, would disappear forever beneath 

 the waters which would now cover the face 

 of a lifeless world." 



British Whales. The whales of the Brit- 

 ish Islands are more abundant and more va- 

 ried in species than has generally been sup- 

 posed. The most important of the species 

 that have occurred in Great Britain is the 

 Greenland right whale, which has now been 

 driven into the far north. The Atlantic 

 right whale was once hunted with consider- 

 able vigor in the English Channel ; and those 

 who hunted it there are said to have invented 

 the harpoon, and taught the Dutch whalers 

 how to use it. The hump-backed or Ber- 

 muda whale has been cast ashore on the isl- 

 ands, and is therefore entitled to be called 

 a British species. A fourth species is the 

 caaing or bottle-nose whale, a large school of 

 which was seen in the summer of 1888 dis- 

 porting in the Bay of Firth. The whale an 

 air-breathing mammal living in the water 

 is admirably adapted to its environment. 

 The blow-holes are placed on the top of 

 the head, and the animal can respire only 

 when they are above the water. The ani- 

 mal heat is preserved and the specific grav- 

 ity reduced by the thick coating of blub- 

 ber that lies just under the skin. An inter- 

 esting trait in the economy of the whale is 

 the manner in which it suckles its young. It 

 partly turns on its side, and the teats being 

 protruded, sucking and breathing go on 

 simultaneously. The "baleen" or whale- 

 bone of the "whalebone whales" consists 

 of about five hundred laminae taking the 

 place of teeth ranged about two thirds of 

 an inch apart, and having their interior 

 edges covered with fringes of hair. Some 

 of them are fifteen feet long. The cavity of 

 a whale's mouth has been compared with 

 that of an ordinary ship's cabin, the inside 

 of which is covered with a thick fur. The 

 soft, spongy tongue is often a monstrous 



mass ten feet broad and eighteen feet long. 

 The whale feeds upon minute mollusks 

 Medusae and Entomostracece with which 

 the northern seas abound. " Opening its 

 huge mouth," says Prof. Huxley, "and al- 

 lowing the sea-water, with its multitudinous 

 tenants, to fill the oral cavity, the whale 

 shuts the lower jaw upon the baleen plates, 

 and, straining out the water through them, 

 swallows the prey stranded upon its vast 

 tongue." 



Standards of Light. It is a delicate mat- 

 ter to obtain an accurate standard of light. 

 Candles are still most relied upon for the 

 tests of comparison, but it is obvious that 

 they are susceptible of great variations in 

 the intensity of the light they afford. Still, 

 if made according to fixed rules, and their 

 burning similarly regulated, they will give a 

 fair approach to accuracy. Various English 

 acts prescribe a sperm candle of six to the 

 pound, and burning at the rate of one hun- 

 dred and twenty grains per hour ; also that 

 the tip of the wick shall be glowing and 

 slightly bent. Gas examiners are not always 

 as particular in the matter as they ought to 

 be, and, by allowing the wick to remain up- 

 right, may obtain a result indicating a gas of 

 slightly more value than it really has. The 

 German Gas and Water Society recommend 

 an amyl acetate lamp, which is not quite as 

 intense as a candle, and is objected to by 

 Mr. W. J. Dibdin as being unsuitable in the 

 color of its light. Dr. Werner Siemens has 

 devised a selenium photometer, the electric 

 resistance of which is exactly dependent on 

 the light falling upon it. The pentane lamp, 

 and the Methven screen, in which a coal-gas 

 light is admitted through an aperture of fixed 

 dimensions, are favored by many persons; 

 and a standard afforded by a melting or a 

 solidifying platinum wire is well spoken of. 



John Mercer, F. R. S. John Mercer has 

 been called by Mr. T. E. Thorpe, in "Na- 

 ture," the "Palissy of calico-printing." lie 

 achieved a great success in the arts without 

 any other helps than those which he made for 

 or attracted to himself. He was born, accord- 

 ing to Mr. E. A. Parnell's "Life," in 1791, 

 the son of a hand-loom weaver, who had 

 turned to agriculture. When nine years old, 

 he was set to work, on the death of his 



