552 



SCIENCE. 



Saint-Gervais and the heights of Belleville. Their quality- 

 leaves much to desire. 



" Essentially selenitic, their hydrometric degree reaches 

 enormous proportions : 100 degrees to 1 50 degrees accord- 

 ing as the waters of Saint Gervais and of Belleville are 

 more or less mingled." They contain very little organic 

 matters, some rare algse and many calcareous crystals. 



The well of Grenelle, become celebrated, was com- 

 menced in 1833 and only finished in 1841. It was on the 

 occasion of its boring that the relations of the elevation of 

 temperature to the depth of the soil observed by Arago 

 and Walferdin, were st ited ; that is to say, with every 32 

 metres the temperature rises one degree. 



The water of the well of Grenelle (fig. 7) lacks oxygen 

 which it can gain in the basins of the Pantheon where it 

 is conducted. This water is limpid, indicates at its out- 

 let about 28 degrees, and is very nearly pure from all or- 

 ganism, since it only contains some traces of mycelium 

 of mushrooms (No. 2) and, here and there, several Di- 

 atoms (No. 1) probably drawn from the tubes through 

 which it flows. The traces of sulphuretted hydrogen 

 which it contains, impairs a little the quality of this water, 

 but not enough to make it unfit for consumption. 



The water of the well of Passy, perforated from 1854 

 to 1861, can be compared with that of Grenelle (fig. 8). 

 The results which the piercing of this well caused are 

 known ; the sale of the water of Grenelle was made con- 

 siderably less. The carbonate of lime, as well as the 

 bicarbonate of potash, are abundant in both. All things 

 equal, moreover, M. Neuville gives his preference for the 

 waters of Passy rather than for those of Grenelle. Sev- 

 eral algae are found in them {CaloihrLx [No. 8], Rhizoclo- 

 niinn [No. 5], Cosmarium [No. 1], Gloeocys'.is [No. 9]) ; 

 several encysted infusoria (No. 2), and a few unimportant 

 organic remains. 



Lastly, the waters of ordinary wells are potable only 

 when they are not found in a great city. The varied in- 

 filtrations, the connection with the soil, and the indus- 

 tries which can contaminate them, aie considerations 

 which must be taken into account in deciding the quality 

 of the waters of wells, and which can render them unfit 

 for consumption. They contain at Paris much of the 

 nitrate and sulphate of lime, and they are also very 

 much charged with organic matters in a state of de- 

 composition ; but of algas there is no trace and there are, 

 here and there, several microscopic crustaceans. It is 

 above all in the neighborhood of cemeteries that the 

 waters of wells should not be used except for gross pur- 

 poses. This advice is upheld by the studies of Mr 

 Belgrand, who has observed that, in the environs of 

 Pere-Lachaise and of the cemetery of Montparnasse, 

 the waters of wells were stocked, above all during the 

 heat of summer. 



Basing his results on microscopical analyses, M. Neu- 

 ville arranges the waters of Paris in the following order 

 to indicate their degree of purity : 1, waters of the Vanne; 

 2, of the Marne at Saint-Maur ; 3, of the Marne at Char- 

 enton ; 4, of the Seine at Port-a-l'-Anglais ; 5, of the 

 canal of Ourcq ; 6, of Arcueil ; 7, of the sources of the 

 Nord ; 8, of the wells of Passy ; 9, of Grenelle ; 10, of 

 the Dhuis ; 11, of the Seine at the bridge of Austerlitz ; 

 12, of a well on the left bank; 13, of the Seine at 

 Saint-Ouen ; 14, at Auteuil ; 15, at Chaillot. 



Tidal Power at Bristol. — At a recent meeting of the 

 Town Council of Bristol a motion was brought forward, 

 but not adopted, that " instructions be given to the sanitary 

 authority to cause inquiries to be made into the tidal power 

 of the Avon with a view to its being utilized for working 

 electric lights for the city, the storage of motive power and 

 other purposes, and that scientific aid be employed for the 

 purpose." 



THE EVOLUTION OF FLYING ANIMALS. 

 By Charles Morris. 



Continued from page 536. 



Yet there is one instance of a leaping animal in which 

 a partial flight has been gained in this manner. We 

 allude to the flying-fish. Whatever first induced this 

 creature to spring from the water through the impulse of 

 its swimming motion — whether the pursuit of enemies, 

 or some other cause — at any rate its fore limbs were 

 already developed into wing-like organs, through their 

 use as fins. The flying-fish does not really fly. But an 

 increased spread of its supporting fins, which act as 

 parachutes, would enable it to make longer leaps, and 

 natural selection has undoubtedly produced this exten- 

 sion of the fins. 



Land animals present us with several instances of this 

 parachute motion. And significantly it never arises in 

 earth-leaping, but always in tree-leaping animals. Among 

 mammals we find three instances of such a habit, in 

 widely separated families, embracing the Flying Squirrel, 

 the Flying Phalanger, and the Flying Lemur. Among 

 reptiles there is one instance, the Flying Dragon. The 

 three mammalian genera mentioned include a number of 

 species, and an imperfect flight is gained in the same 

 manner in every case. During their so-called flight the 

 limbs are extended almost at right angles to the body, 

 and the skin of the sides has been developed until it is 

 expanded into a broad membrane between these limbs, 

 which, in the case of the Flying Lemur, extends from 

 the nape of the neck to the tail. In their bold leaps from 

 the branches of trees these creatures are partly supported 

 by their membraneous wings, so that they descend slowly 

 and easily. Some of them can even slightly vary the di- 

 rection of their motion, so as to pursue insects. 



The flying reptile, the little Draco Volans, gains its 

 support in a somewhat different manner. In this case 

 the extended membrane is supported, not upon the limbs 

 but upon the false ribs, which grow out horizontally from 

 their vertebral connection to a considerable distance, 

 giving the animal a wing-like expansion of its sides. 



We may readily conjecture the method in which such 

 an organization was gained. The smaller tree dwelling 

 animals are exposed to attacks from foes, the same as all 

 other animals. Or, if carnivorous, they need to pursue 

 their prey. In both these cases the power to make long 

 leaps from branch to branch, or from tree to tree, is so 

 obvious an advantage, that it is not surprising that many 

 animals have become very bold and skillful in this par- 

 ticular. Many of these animals have also the habit of 

 crouching on the branches of trees for concealment, their 

 legs being extended side-wise, and their bodies flattened. 

 This position of the legs in rest would most probably be 

 retained during the leaping motion in which they are not 

 employed. If, then, in any case, the width of the body 

 should be increased, as by a chance extra expansion of 

 the skin of the sides, supported by the outstretched 

 limbs, the animal would be borne up by the, air, and 

 could make a longer leap. Such a conformation would 

 aid it in flight or pursuit, and natural selection must op- 

 erate to retain any such special advantage of form. It 

 certainly seems very probable that the supporting mem- 

 brane of these creatures was thus developed, and that 

 the Flying Dragon gained its rib expansion through a 

 similar process. 



These cases may seem of little importance in an inves- 

 tigation of the origin of the flying power in birds ; yet 

 they are, in reality, of considerable importance. They 

 point significantly to the most probable method of flight 

 development, namely, as the result of an original leaping 

 habit, from branch to branch or from tree to tree. Al- 

 though the above cases are instances of parachute mo- 

 tion only, not of true flight, yet we have strong reason 

 to believe that the earliest flying animals gained their 

 power of flight as a direct extension of the above method. 



