HARDWICKE'S SCIENCE-GOSSIP. 



quently found in the later deposits, as well as in 

 the cave breccias. An almost arctic flora covered 

 the plains, and crept up the hill-sides as far as the 

 then perpetual snow-line. Glaciers still debouched 

 through the mountain defiles into the plains, and 

 moraines, or heaps of angular stones, thrust forward 

 by the advancing foot of the glacier, still remain 

 in Scotland, Cumberland, and Wales, to indicate 

 how far these glaciers travelled. Where the ice- 

 sheet descended from the mountains, of course 

 there was the greatest amount of pressure. Here 

 great hollows were scooped out of the hard, solid 

 rocks, and these hollows are now filled with fresh 

 water, and form the lakes of North Wales, Lan- 

 cashire, and Cumberland, and, on the Continent, in 

 Switzerland. The Swiss glaciers, by the way, were 

 then much more extensive than they now are. At 

 present their growth is impeded by a warm wind, 

 which accumulates over the Desert of Sahara, in 

 North Africa. But, at the time of which I speak, 

 the Sahara was a sea, as is indicated by the abun- 

 dance of ordinary cockles and mussels found a few 

 feet below its terrible drifting sands. Then, no 

 warm wind could form, and the European glaciers 

 grew unchecked. Again, the temperate mollusca, 

 such as oysters, cockles, mussels, &c, had migrated 

 from our latitudes, and taken up their abodes in 

 seas which, although farther south, represented iu 

 glacial times, as far as tbe temperature was con- 

 cerned, the seas of Great Britain. 



As the climate became warmer, the arctic plants 

 left the lowlands, where they became extinct. Their 

 places were taken by a more southerly flora, which 

 had set out from Asia Minor, and covered the 

 greater part of Europe. The arctic plants occu- 

 pying the highest grounds, therefore, were the only 

 remains of this once widely-spread arctic flora, 

 which could find suitable and fitting circumstances 

 amid which they could live. And here the wan- 

 dering botauist now finds them — living proofs of 

 the truth of what I have been saying respecting 

 the long arctic winter of the northern hemisphere. 

 Subsequently, Ireland was separated from the Con- 

 tinent, England having been cut off some time 

 before. When the climate had toned down, man 

 appeared on the scene. His weapons are found in 

 the most' recent of deposits, and his bones beneath 

 the stalagmitic floor of limestone caves. The 

 woolly-haired Elephant and Rhinoceros disappeared 

 for ever; the Glutton, Lemming, Reindeer, &c, 

 like the arctic plants, migrated with the decreasing 

 cold into northern regions. Meantime, the bottom 

 of the glacial sea had become dry land. The old, 

 hard, and barren rocks had been thickly strewn 

 with rich subsoils, the very elements necessary for 

 agricultural purposes. Nature had done, by means 

 of her glacier and other action, exactly what the 

 scientiGc farmer sometimes docs when he adds 



artificial manure to improve his soils. She had 

 ground and pounded all the older rocks to make up 

 a new compound that should possess all their 

 valuable mineral ingredients. In this way only 

 could mankind have been blessed with the necessary 

 elements for the purposes of husbandry. Thus, in 

 comparison with other periods, that when man was 

 introduced was especially favoured. 



URASTER RUBENS. 



A S marine aquaria are now so well known and 

 ^--*- so widely distributed, it seems a pity that 

 people with such means at their disposal should 

 not undertake the keeping and study of the more 

 delicate animals of our seas and shores ; as, by such 

 means, many disconnected facts and observations in 

 natural history may be linked together in a manner 

 to be understood. The difficulty of obtaining ani- 

 mals inland is no doubt often a bar to their suc- 

 cessful study, as they must be in a healthy condition 

 when placed in the tank. My own observations 

 have not been so numerous as I could wish, I not 

 having been able to obtain many objects in a suffi- 

 ciently healthy state to live. I refer more particu- 

 larly to the Echiuoderms. This great class, which 

 is entirely marine, contains some of the most beauti- 

 ful and graceful animals that are known. But I have 

 now to describe the more common member of this 

 class, Uraster rttbens. 



The animal of which 1 now speak belongs to the 

 sub-family Urasterina, distinguished by having four 

 rows of suckers in each of the ray-avenues. The 

 body of this Echinoderm, which is a slightly elevated 

 disk, is elongated into five stout arms or rays, which 

 are rather rounded, and are really extensions of the 

 body, of which they form part. It. is enclosed in a 

 toughish skin, in which are imbedded calcareous 

 plates of various shapes, rather closely congregated, 

 so as to form a strong skeleton. In certain situa- 

 tions all over the dorsal surface, these plates are 

 raised into strong spines, which give the star-fish 

 that prickly feel when handled. The arrangement 

 of these large spines does not seem to be after any 

 particular order : three sets of long spines border- 

 ing the avenues especially characterize the genus. 



The avenues on the under side of the rays are 

 filled with the ambulacra. These are fleshy arms 

 furnished with suckers at their extremities, by which 

 the animal can attach itself, and are used as organs 

 of progression. They are very contractile, and 

 highly sensitive, as by a slight touch, when the 

 animal is in repose and the arms are almost motion- 

 less, we can set them all in motion. 



But let us examine the animal more closely by 

 means of the microscope, to do which we must 

 select one that will go conveniently into a large 



