October 31, 1884. 



SCIENCE, 



421 



HOW FAR A LIGHT MAY BE SEEN 

 UNDER WATER. 



Me. Edouard SaeasijST recently made an interest- 

 ing report of the experiments of the committee of the 

 physical society of Geneva, in regard to the transpar- 

 ency of the water of the lake. The auxiliary society 

 of Geneva generously gave the committee twenty-five 

 hundred francs to aid in the researches; and Messrs. 

 Soret, Sarasin, C. de Candolle, H. Fol, A. Killiet, Ch. 

 Soret, Plantamour, and K. Pictet took part. Three 

 candles in a lantern (the flame being fed by a con- 

 tinuous current of air) are visible, at a depth of thirty 

 metres, in the pure water of the lake. An electric 

 light was distinctly seen in the water at the foot of the 

 hydraulic machine of Geneva at a depth of thirty-three 

 metres. A few centimetres more caused the clear im- 

 age to disappear, which was replaced by diffuse light, 

 faintly perceptible at sixty-seven metres. Messrs. 

 Sarasin and Soret noticed a very characteristic ab- 

 sorption ray in the spectrum of light which had trav- 

 ersed a certain layer of water. This ray had been seen 

 before, but former publications had not attracted the 

 attention of physicists. The recent observations con- 

 firmed the fact, and completed the data already ob- 

 tained. This ray is in the red, near B. The same 

 physicists have also undertaken experiments upon 

 the transparency of water when agitated with insolu- 

 ble substances, such as the chloride of silver, etc. 

 They find that the distance of clear vision varies very 

 little with the increase of the brilliancy of the lumi- 

 nous body and its absolute dimensions. Assisted by 

 Dr. Marcet, the committee has made photographic 

 experiments in the deep portions of the lake. Down 

 to two hundred and fifty metres they find the effect 

 of light on the sensitive plates; but this depth seems 

 to be, at least for the plates now in use, the extreme 

 limit of action of the sun's light. Below this point 

 the lake is a vast, dark chamber. 



THE MERIDIAN CONFERENCE. 1 



At the meeting on Wednesday, the 22d, the work 

 of the conference was finished so far as the trans- 

 action of new business is concerned. Gen. Strachey 

 withdrew his resolution for ten-minute meiidians for 

 local time, and the conference then proceeded to pass 

 a resolution reciting and affirming its action upon the 

 seven resolutions already adopted. These, as finally 

 determined upon, are as follows : — 



1. " That it is the opinion of this congress that it 

 is desirable to adopt a single prime meridian for all 

 nations, in place of the multiplicity of initial meri- 

 dians which now exist." 



2. "That the conference proposes to the govern- 

 ments here represented the adoption of the meridian 

 passing through the centre of the transit instrument 

 at the observatory of Greenwich, as the initial meri- 

 dian for longitude." 



3. " That from this meridian, longitude shall be 



1 Concluded from p. 406. 



counted in two directions up to 180°, east longitude 

 being plus, and west longitude minus." 



4. " That the conference proposes the adoption of 

 a universal day for all purposes for which it may be 

 found convenient, and which shall not interfere with 

 the use of local or other standard time, Where desir- 

 able." 



5. " That this universal day is to be a mean solar 

 day; is to begin for all the world at the moment of 

 mean midnight of the initial meridian, coinciding 

 with the beginning of the civil day and date of that 

 meridian ; and is to be counted from zero up to twenty- 

 four hours." 



6. " That the conference expresses the hope, that, 

 as soon as may be practicable, the astronomical and 

 nautical days will be arranged everywhere to begin 

 at mean midnight." 



7. " That the conference expresses the hope that 

 the technical studies intended to regulate and extend 

 the application of the decimal system to angular 

 measure, and to that of time, shall be resumed, so as 

 to permit the extension of this application to all cases 

 where it presents real advantage." 



A final resolution was then passed, reading as fol- 

 lows : — 



" That a copy of the resolutions passed by this con- 

 ference shall be communicated to the government 

 of the United States, at whose instance, and within 

 whose territory, the conference has been convened." 



With a hearty vote of thanks to the government 

 for the facilities offered, to the president, Admiral 

 Rodgers, for his impartiality and courtesy, and to the 

 secretaries for their faithful work, and with a suitable 

 response by the president, the conference adjourned, 

 subject to the call of the latter, for the purpose only 

 of verifying the protocols of the proceedings. 



The phraseology of the seventh resolution is some- 

 what peculiar ; and the word ' resumed ' looks very 

 much like a mistake in translating ' re'sumer,' as the 

 resolution was introduced by the French delegates. 



THE RESOURCES OF THE UNITED 

 STATES. 



The seventh quarto volume of the Tenth 

 census, containing the tables of valuation, 

 taxation, and public indebtedness, must be re- 

 garded as the most exact, and one of the most 

 valuable, yet issued. It is largely historical in 

 its treatment of the subject, which allows an 

 exact historical statement more readily than 

 most of the subjects of these A r olumes ; and it 

 thus presents a view of the finances of the 

 United States for a century, which must be of 

 great interest to all economists. There is also 

 much information of a political and personal 

 nature contained in the history of the foreign 

 loans made by the United States and by indi- 

 vidual states, including some description of 

 the repudiated debts of Pennsylvania, Missis- 



