SCIENCE. 



549 



replaced by others in places where a different industry was 

 in operation. 



It is in this same order of ideas that the Administrator of 

 Bridges and Roads of the Seine and Oise sent us lately a 

 difficult question to answer. The question was to disinfect 

 a river on the environs of Beaumont, which, during the 

 heat of summer, was poisoned by a cryptogam of the 

 genus Leptothrix. This vegetable is an aquatic and fila- 

 ceous fungi which thrives and grows on the refuse 

 of factories. The only answer to make was the well- 

 known axiom : sublata causa tollitur effectus. 



M. Neuville, the author of the memoir of which we are 

 treating, is astonished that a work similar to that which he 

 has undertaken, has not yet been done for the waters of 

 Paris, whose sources are different, and which, con- 

 sequently, do not present an equal degree of purity. 

 Placing himself in a purely utilitarian point of view, he 

 seeks to enlighten the administrator and the public on one 

 of the indispensable sources of nourishment, that is to say 

 the water consumed each day, by making use of his 

 knowledge of cryptogams, and chiefly those of the family 

 of Diatoms, for the study of which he had a predilec- 

 tion. 



The complete purity of water is not always on account 

 of the greater or less number of organic matters that it 

 contains ; it must be that these matters have a purifying 

 character in themselves, and this condition obtains only 

 when they are living vegetable growths, containing chloro- 

 phylle or green matter, having the property of freeing the 

 oxygen which is dissolved in the water, on the one hand, 

 and of absorbing, on the other, the carbonic acid gas which 

 makes the water unfit to drink. Aquatic plants, then, are 

 useful to the water which gives them shelter, yet with the 

 condition that their bodies do not, by their accumulation, 

 counterbalance the salutary effects. 



Another cause very often acts to give water unhealthy 

 properties. The lime salts which it holds in solution, and 

 sometimes in-great quantity, cause troublesome and some- 

 times serious diseases. The carbonate, but above all the 

 sulphate, of calcium, makes the waters selenitic, as it is 

 said, and then they become unfit for the cooking of vege- 

 tables, do not dissolve soap, and are indigestible. It is 

 possible, however, for water to dissolve soap and never- 

 theless to cook vegetables ; this occurs when in place of 

 sulphate of calcium it contains magnesium. 4 



The waters of the source are often sought after for 

 their limpidity and freshness, which does not always imply 

 that they are really potable ; it is even probable that 

 if the waters of our rivers were taken at their source 

 they would not have the qualities which they acquire 

 after a journey of several miles. But when these rivers 

 pass through an important manulacturing city, the injec- 

 tions, the impurities of all sorts which they receive will 

 rapidly change their qualities; stocked, so to speak, 

 in the passage by the city, they are yet able to 

 improve themselves somewhat after a new journey in the 

 country, which permits them to deposit the foreign mat- 

 ters which contaminate them. There are these elemen- 

 tary considerations which should always insist that the 

 waters which supply a city should be taken above and 

 not below the city. 



Borrowing from the interesting works of M. Miquel, 

 the savant of the Observatory of Montsouris, whatever 

 they contain of use to his work, M. Neuville, among 

 other things, reproduces the following table of compari- 

 son for the use of the reader, and shows what organisms 

 the waters from the source and of different qualities can 

 contain, observed with considerable magnifying power: 



"A microscopic exam, of water ... of London, 1850. 



"Remarks of some Algae found in the water ... of Boston, 1877. 



c Rapport sur l'alteration, la corruption et l'assainissement des riv- 

 itres, 1873. 



d Translated from La Nature. 



PROPORTION OF LOW ORGANISMS CONTAINED IN DIFFERENT 

 WATERS. 



Microbs by 

 hund. cube. 



Water of condensation 0.2 



Rain water 35.0 



Water of the Vanne 62.0 



" " Seine, in Paris 1200.0 



Sewer water 20000.0 



It is indispensable that analyses of this nature should 

 be made rapidly, because in a short time the microbes 

 grow in a great degree, and will no longer give exact 

 figures. 



The method which M. Neuville has followed does not 

 consist of chemical analyses of the waters of Paris, 

 which had been done long before by well-known sci- 

 entists ; it is rather a kind of statistics of the foreign mat- 

 ters contained in each of them, and which the use of 

 the microscope reveals. 



The waters submitted to his examination are those of 

 the Marne, taken at Saint-Maur and Charenton ; of the 

 Seine, at the Port-a-l'Anglais, at the bridge of Auster- 

 litz, taken at Chaillot, Auteuil, and at Saint-Ouen ; the 

 waters of the canal of Ourcq, of the Vanne, of the 

 Dhuis, of Arcueil, of the sources cf the Nord of Paris, 

 of the artesian wells at Grenelle and Passy, finally that 

 of a well of the left bank of the Seine. 



A constant quantity of five litres of water was taken at 

 the middle of the above-mentioned streams, or at the 

 inlet of the waters of the sources ; then after a settling of 

 12 hours, by means of an appropriate siphon, he decanted 

 until it was reduced to 300 grammes. The contents were 

 turned into a graduated gauge and after rest, by the use 

 of a small pipe be gently raised the liquid in order to 

 leave but a deposit of two to three centimetre cubes. It is 

 this deposit which is directly submitted to microscopical 

 observation, after having been put in cellular preparations 

 before being preserved. Observation was made on 

 a determined number of preparations, all sketched in a 

 light room, and the sum of the latter serves to form one 

 of the plates which accompany this article, which con- 

 tains seventeen. A diagram, or schematic table, indicates 

 the result of chemical analyses and of microscopical 

 observations made for the Seine in its journey through 

 Paris. 



The water of the Marne taken at Saint-Maur, is 

 relatively rather pure ; yet organic matters are found 

 in great abundance in it ; but they are, above all, living 

 matters, and more purifying than corrupting (Fig. ft) 

 They are a part of the Desmids in the gteen matter and 

 belong to the genus Pediastrum (No. 9) or Raphidium 

 (No. 10) ; or else cf filaceous algae (No. 11) of the genus 

 Ulothrix. On the other hand, and much more abundant 

 are the Diatoms with silicious carapace, and, for the most 

 part, gifted with movements of translation very curious 

 to observe. Such are the genera Sirurella (No. 1), 

 Nitzschia (No. 2 and 3), Cymatopleura (No. 4), Cynedra 

 (No. 5), Diat07tia (No. 6), Pleurostgrna (No. 7), etc., or 

 even Infusoria (No. 13), which make prey of several of 

 these small growths ; but, above all, the organic re- 

 mains. Finally the mineral matters which, in the water 

 of the Marne river, are always more or less muddy, form 

 the small chrystalline groups in the preparation (No. 15). 

 This water is then very good ; but on approaching its 

 confluence, that is to say, at Charenton, not only the 

 Diatoms are increased in number, but the Infusoria 

 abound in it as well as detritus, which probably is due 

 to the inhabitants of the Marne at this place. 



In the water of the Seine taken at the Port-a-l'Anglais 

 (fig. 2), a very great proportion of organisms is found. 

 This point of the river, intended at one time to furnish 

 Paris with a very potable water, has lost its value on ac- 

 count of the factories and manufactories which are built 

 on it above the city, and the length of the small streams 

 of water which it receives in these places. Desmids are 

 found in it the genus Closterium (No. I), Scenedesmus 



