198 THE MICROSCOPE AND ITS LESSONS. 



In that interesting voyage of the Challenger, the con- 

 tents of many boxes of ooze were brought up from sound- 

 ings ranging from 50 to 4750 fathoms for that almost 

 incredible depth was reached as the ship was crossing 

 from Japan to the Society Islands in the Pacific. 



A fathom is equal to six feet, and there are 5280 feet 

 in a mile, so the greatest ocean-depth that has yet been 

 known to have been reached is very nearly five miles and 

 a half; and what does it reveal? 



Look ! the diameter of the little circle on our object 

 now before you is only half an inch, and yet in that small 

 space there may be thousands of the most lovely forms, 

 from the spicules of sponges to those exquisite Polycystina 

 which astonish and delight all who have eyes to see ; and 

 there, again, is that marvellous medal of creation, not 

 larger than the point of an ordinary-sized pin in its cir- 

 cumference, the disc, called, after its spider-web-like 

 pattern, the Arachnoidiscus. 



" The works of the Lord are great, sought out of all 

 them that have pleasure therein ; " and what does our 

 "searching" among these lovely inhabitants of the 

 deepest of seas, invisible as they are to our unaided 

 eyes, tell us? That flint and chalk are the two chief 

 mineral ingredients which God has employed in the 

 composition of ocean-depths and mountain-heights; for, 

 observe, Foraminifera, sponge spicules, Polycystina, and 

 Diatomacese are found in a recent, as, forming solid 

 masses, they are discovered in a fossil state. 



These infinitely little creatures, whose bodies, many 

 years after they ceased to live, became fossilized by 

 an infiltration of lime, thus changed to what we know as 

 "chalk," still preserving their beauty of form, each 

 taking its part in the formation of huge sub-aqueous 

 masses, which, afterwards, by mighty subterranean forces 



