THE YOUNG NATURALIST. 



143 



the result will be that the liquid will begin 

 to " blubber." The acid liberates carbonic 

 acid gas, which is one of the chief con- 

 stituent parts of the three substances 

 named. 



In the process of burning, or rather 

 roasting lime parts with its carbonic acid, 

 and quick lime remains which is so valuable 

 in building purposes. The formation of 

 limestone rocks is very different from that 

 of most other rocks. Sandstone, for in- 

 stance, is the result of wear and tear of 

 older sandstones, the rain and atmospheric 

 influences, crumble away the rocks on the 

 mountain side, and the debris is washed down 

 to the river and carried on to lakes, and goes I 

 to form other rocks. The origin of lime- 

 stone is entirely different. How then 

 do those thick beds of limestone come, 

 which, in some parts of England, are 1500 

 feet thick ? Where does this vast accum- 

 ulation of rock come from ? I have to I 

 place before you the assured conviction, 

 now accepted by all geologists, that the I 

 carbonate of lime of which they are formed, 

 has been derived from the sea, and ! 

 deposited at the bottom by very minute | 

 animals. The results of the investigations 

 of the " Challenger " has shown that such 

 a substance is now accumulating at the 

 bottom of the Atlantic. These minute 

 animals make their shells of this carbonate j 

 of lime which they derive from the sea, 

 (see Y.N. p. 33) and when we let down the 

 linewe come first to living animals, then to 

 dead animals, and finally to a very fine 

 mud, produced by the breaking up of these 

 shells. These animals are very minute, yet 

 I have no hesitation in saying that I believe 

 there is more life in these Atlantic beds 

 than there is im all the world beside. 

 These little animals are not all that have 

 produced limestones. In some tropical 

 countries there are what are known, as coral 

 reefs, (see Y.N.p. 44) which are made of the 

 same kind of substance — carbonate of lime, 

 and we have in the neighbourhood of Bristol, 



limestones which unquestionably have been 

 coral reefs. What relation does the mar- 

 ble bear to limestone ? We have ample 

 proof that it is volcanic agency which oblit- 

 erates all the former characters of limestone 

 and changes it into marble. Many beds 01 

 limestone show no traces of its organic 

 origin, while others are completely com- 

 posed of fossils, and these latter could not 

 have been formed by the wearing down of 

 older limestone rocks. In the centre of 

 Scotland is a great platform of limestone, 

 the edges of which have been contorted by 

 volcanic action. In the centre of this bed 

 the organic origin is plainly visible, but 

 around the edges no fossils exist, and the 

 character is entirely changed. In Russia, 

 where the country is almost a dead level, 

 and where the ground has not been up and 

 down like our corner of Europe, the organic 

 characters of the limestones are well pre- 

 served. The lecturer then had thrown 

 upon the screen beautiful photographs of 

 the different kinds of animals the shells or 

 skeletons of which goes to constitute lime- 

 stone. He referred to the pleasures a 

 study of nature gave to men. He had met 

 with men who were closely imprisoned in a 

 shop from morning till night, yet some of 

 these, when a spare hour or two presented 

 itself, would take their hammer and ramble 

 out to some neighbouring quarry, and these 

 men found the utmost delight in these ram- 

 bles. When he was on a collecting excursion 

 at Redcar, he used to see the visitors come 

 there, many of them withno apparent pur- 

 pose, and he used to get one or two together 

 and talk to them about some natural object, 

 and he found that such a course was often 

 very instrumental in setting them out on an 

 enquiry on their own account. That was 

 just the purpose these Gilchrist Lectures 

 were intended for, they wished to stir up an 

 enquiring spirit in natural history ; and he 

 believed that people who were once engraft- 

 ed into such studies never forsook them 

 altogether. 



