42 



NATURE 



[November 8, 1894 



they are of apparency nearly unirorm width throui;hout their 

 length. What they are is another matter. Mr. Lowell thinks, 

 however, that the mere aspect is enou:;h to cause all theories 

 about glacia'iun lissures or surface cracks to die an instant and 

 natural death. 



Bat it is their singular arrangement that is most suggestively 

 impressive. They have every appearance of having been laid 

 out on a definite and highly economic plan. They cut up the 

 surface of the planet into a network of triangles instantly sug- 

 gestive of design. \Yhat is more, at each of the junctions there 

 is apparently a dark spol. This feature seems to be invariable, 

 as, on closer appioach, junction after junction turns out to have 

 one. The larger of these appear on Schiaparelli's chart as 

 lakes. But there would >eem to be a small infinity of smaller 

 ones. A short half-hundred of them were seen at .\requipa in 

 1892, and others have recently been detected at Flagstaff. For 

 example, an important new canal, which runs from the western 

 end of the sea of the Sirens to Ccraunius, and which in view of its 

 pointof departure Mr. Lowell is induced to call the Ulysses, passes 

 through three of these small dark spots on the w.ay, one at each 

 junction. One of these was seen at Arequipa and elsewhere 

 in 1S92; the other two are new discoveries. The region of 

 the Lake uf the Sun is especially fertile in canals. In one of 

 the drawings which accompanies the paper here summarised, 

 thirty-one canals are to he seen, counting each line between 

 junctions ss a separate canal. Of these seventeen are amon ; 

 those in S>;liiaparelli's chart, while fourteen are not. Of the 

 twelve lakes m the figure, five are not down on his chart. This 

 is thought not, in general, to be the result of change, though 

 changes there apparently have been after proper discount has 

 been made for dilTerence of observations and of drawing. First 

 and foremost, the Golden Chersonese has vanished ; the land 

 of Ophir now forms the continental coast-line. Secondly, 

 Icaria has entirely altered in contour, resembling now an open 

 fan about the Phccnix lake for pivot. Pli.-eioniis has shrunk 

 to one-third of its former width — as represented in Schiaparelli's 

 chart. Eosphoros no longer enters Phoenix lake at the point 

 opposite Pyriphlegeihon, but farther to the west. Hut the 

 strangest transformation of all is that of the Phasis, which has 

 apparently obligingly become two (not geminated in the 

 technical sense) to suit both the old and the new state of 

 things. There is now a canal running in the same direction as 

 the old Phasis, but not to the southern end of Phxnontis ; and 

 there is another one running to the southern end of Phxtontis, 

 but not in the same direction as heietofore. This attempt to 

 carry out two apparently important ends by self-multiplication 

 is not a common characteristic of inanimate nature — a point 

 which Mr. Lowell holds is worth consideration. 



Mr. A. Stanley Williams contributes lo the November 

 Oliienatoiy an account of his observations of Murs up to 

 October 20. With regard to the canals Mr. Williams says: — 

 " By taking advantage of every favourable opportunity, fifty- 

 one canals have been observed up to the present time [Oc' ober 20]. 

 These include most of ihose shown in Prof. Schiaparelli's latest 

 map that could be properly observed at present, and in addition 

 thiec ihers not maiked in the map. Generally speaking there 

 is no difficulty in certainly identifying the canals, wiih the 

 exception of a few which are situated far north, and con- 

 nequently arc loo close lo the limb to be distinctly observed. 

 The general accuracy of the map is very sti iking, and I have 

 often been strongly impressed by the very thorough manner in 

 which Prof. Schiaparelli's work has been done. It is most rare 

 to come across the trace of a canal not marked in his map, 

 and the posilions of objects arc usually very reliable." 



In the October number of our contemporary, Mr. Williams 

 stated that Phison was probably double. Later observations, 

 however, have shown it to be only single, the apparent gcmi- 

 nalion being probably caused by the existence of a feeble, 

 unrccoided canal running paiallcl to it, and about midway 

 between it and the coxst bordering the Kaiser Sea. Agatho- 

 dxnion and Ainxes were seen intensely double on three or lour 

 nights in September. Chrysorrhoas was also seen double, but 

 thiA canal appeared as an inconspicuous object comparcrl with 

 Agaihodxmon and Ataxc. In .September Mr. Williams saw 

 AiDenihet at a narrow inconspicuous and apparently single 

 canal. At ihe beginning of dclobcr, however, the object 

 appeared as a very brr>a<i, dusky, double canal. Ganges is 

 another broad, cons))icu<>us double canal, ihe duplicity of which, 

 accoKling lo Mr. Williams, is so obvious .as to be apparent 

 on almost any night on which obtcrvations are potiible. 



Referring to the small dark spots designated lakes, Mr. 

 Williams says: — "Several more of these curious dark spots 

 have been seen. Lacu~ Phoenicis on a good night appears as 

 a small, nearly round, almost black spot, resembling the shadow 

 of a satellite of Jupiter when in transit. On one night a feebler 

 companion spot was seen just preceding it. Lacus Tilhonias is 

 a similar definite and nearly black spot, with a feebler com- 

 panion following it. In a fine drawing of Mars, dated Septem- 

 ber 5, Mr. Cammell shows Lacus Moeris as a minute datk spot, 

 with Nepenthes as a narrow definite line, and so I have ■■een 

 them on several nights lately. Lacus Tritonis is a similar 

 spot. At the junction of the canals .■\menthes (following com- 

 ponent), Thoth, and Astapus, there is also a little dark spot. 

 The dark spot at the north end of the Ganges, known as Lacus 

 Luna;, has been rather perplexing. On several nights there 

 was an evident appearance of duplicity about it, though it was 

 impossible to say with certainly in which direction it was double. 

 .\t length, however, the mystery was cleared up, the lake 

 having been seen distinctly double on September 29 at right 

 angles to the direction of the Hydraotes. The streak or bridge 

 dividing the lake into two was bright yellow." 



The varying appearances presented during October by the 

 Mare Cimmeiium, and the extensive region lying to the north of 

 it, leads Mr. Williams to think that a great development of 

 cloud or mist has lately taken place on Mars. His observations 

 suggest "that cloud and mist formations are much more ex- 

 tensive and common on Mars than is generally considered to be 

 the case." 



THE ELECTRIC CONDUCTIVITY OF PURE 

 WATER. 



"T^ME difficulties besetting the preparation of water free from 

 •'■ the last traces of dissolved impurity cannot be better 

 illustrated than by the attempts which have been made to .tscer- 

 tain the electric condutiivity of the pure liquiil. At the outset 

 it has to be remembered that the conductivity of water is ex- 

 ceedingly small. As the result of the most recent observations it 

 has been found that one millimetre of water has at o' almost the 

 same resistance as 40,00x3,000 kilometres of copper cf the same 

 cro-s-seclioii ; consequently a copper wire having the same re- 

 sistance and sectional area as one millimetre of water would be 

 long enough to encircle the earth one thousand times. From 

 the difficulty of preventing the introduction of small quantities 

 of dissolved material into ihe water, and from the large diminu- 

 tion which such impurities exercise upon the resistance, there is 

 proljably no physncal constant for which such widely varying 

 values have been given as for the electric conductivity of water. 

 If the conductivity of mercury be taken as 10"', prior to 1S75, 

 the followin;j values had been ascribed to water by the 

 observers named ; — 80, Pouillet ; 70, Hecquercl ; 15, Oberbeck ^ 

 4'S, Koseiti ; 216, Quincke; and \"a, Magnus. In 1875, 

 Kohlrausch succeeded in reducing the observed conductivity to 

 071, or a value only i/i2oth of that given by Pouillet. The 

 large diminution thus brought about was no doubt due, for the 

 most part, to the improved methods employed in obtaining 

 purer samples of water. In Kohlrausch's experiments pains were 

 taken not only lo remove organic matter and any volatile 

 alkaline or acid impurities from the water, but also to ensure 

 that in its subsequent treatment contact with glass was avoided, 

 the purified water being distilled through a platinum condeiiser 

 into a platinum resistance-cell. The next important modifica- 

 cation in the treatment of tlie water was again introduced by 

 Kohlrausch in 1S84. The whole of the above measurements haJ 

 been made upon water distilled under ordinary conditions, and 

 thus in presence of air; he therefore proceeded lo ascertain what 

 alteration in conductivity took place when the water was 

 rendered air-free. For this end he employed a glass apparatus 

 resembling in construction the so-called "water-hammer." A 

 glass bull) of some liOcc. capacity, which served as a retort, 

 was connected by a glass tube with a small glass receiver fitted 

 with platinum eltclrodes. In this receiver the resistance of the 

 waler was measured by the use of a galvanometer and a con- 

 tinuous current, as the latter was so feeble that no appreciable 

 effect was produced by polarisation. The glass connecting-tube 

 was provided with a vertical branch, through which waicr, or 

 liquids 10 clean the appar.alus, could be; introduced. Having 

 admitted a quantity of purified water into the bulb, the vertical 

 lube was then connected with a mercury air-pump, the pump 



NO. 1306, VOL. 51] 



