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QUESTIONS FORMING A COMPLKTE INDKX. 



LESSON XLV. 



Light, why is the apparent depth 

 of water always deceptive ... 479 



Light, why are some substances 

 opaque to it ... ... ... 511 



Light, how do we know that bod- 

 ies reflect it in every direction ... 517 



Light, meditation on 517 



Light and heat, what are the differ- 

 ences between 540 



Light and heat, are they combined 

 in the sun's rays 541 



Light and heat, how do we know 

 that they are separate elements 542 



Light and heat, in what respects 

 are they similar 543 



Light and heat, in what respects 

 are they dissimilar ... ... ... 544 



Light, what is polarized 549 



Light, what is the velocity of arti- 

 ficial 546 



Light, at what rate does the light 

 of the stars travel 547 



Light, why does it tarnish silver ... 553 



Light, why does it affect colours ... 554 



Light, why can pictures be taken 

 by the sun's rays 555 



Light, when does it scorch plants 558 



Lightning, what is the cause of ... 580 



Lightning, why does it sometimes 

 become zig-zag 586 



Lightning, why is it sometimes 

 forked 587 



LESSON XLVI. 

 ing, why is it sometimes like 

 lurid sheet -... 58$ 



Lightning, when is the flash straight 587 



Lightning, when does the flash ap- 

 pear blue 591 



Lightning, why is it sometimes 

 red, at others blue, yellow, or 

 white 592 



Lightning, does it ever pass from 

 the earth to the clouds 593 



Lightning, does it pass from the 

 clouds to the earth 594 



Lightning, what is the force of ... 595 



Lightning, why is it dangerous to 

 stand near a tree during a storm 5S6 



Lightning, why is it dangerous to 

 sit near a fire during a storm ... 598 



Lightning, why is it dangerous to 

 be near water during a storm ... 599 



Lightning, are iron houses danger- 

 ous ... , 600 



Lightning why does it seize upon 

 bell wires, <fcc. ... 601 



Lightning, are umbrellas with steel 

 framea dangerous ... ... ... 603 



Lightning, are iron bedsteads dan- 

 gerous 604 



Lightning, what is the safest situa- 

 tion during a storm 606 



Lightning-conductors, do they at- 

 tract electricity 608 



LESSON XLVII. 



Lightning-conductors, which is the 

 best metal for 610 



Lightning-conductors, why have 

 they sometimes been found inef- 

 fective 609 



Lightning-conductors, why should 

 large buildings have several ... 611 



Lightning-conductors, why should 

 they have several branches pen- 

 etrating the earth 612 



Lightning, through what distance 

 will its light penetrate ... ... 622 



Lightning, how may we calculate 

 the distance of a storm 623 



Lightning, why is the flash gener- 

 ally succeeded by heavy rain ... 626 



Lightning, why is a flash generally 

 followed by a gust of wind ... 627 



Lime-kilns, why do persons viewed 

 through the hot air of, appear 

 distorted and tremulous ... ... 483 



Limpets, why is it difficult to strike 

 them from rocks 665 



Lips, why are they red ... ... 913 



Liver, what effect has it upon the 

 circulation 901 



Looking-glass, why, if you hold one 

 at an~angle towards the sun, will 

 light be thrown in an opposite 

 direction 208 



Loss, is there any such thing in 

 the operations of nature 270 



LESSON XL VIIL 

 Lungs, why are they placed in the 

 chest of the body 932 



Magnetism, what is it 633 



Magnetic bodies, what are they ... 634 



Magpie, why is a single one said to 

 foretell bad weather 1118 



Mahogany, what is it 1190 



Mahogany and other woods, why 

 are there curious markings in ... 1273 



Man, why is he born without a 

 covering 1034 



Man, why has he no external ap- 

 pendage to his mouth 1037 



Marbles, why do they revolve when 

 propelled along the ground ... 818 



Marbles, why do striped appear to 

 hnve more stripes when they are 

 rolling than when at rest ... ... 819 



Marbles, why do they rebound when 

 dropped upon the pavement ... 820 



Marbles, why do they roll furthest 

 upon smooth surfaces ,.. ... 821 



Marbles, how many forces contrib- 

 ute to stop their rolling 882 



Marbles, why do the stripes upon 

 them disappear when they are 

 spinning rapidly ... 823 



Marbles, why are the rings upon 

 them most perceptible at the' 

 " poles," while they are spinning 824 



