328 ANNUAL OF SCIENTIFIC DISCOVERT. 



winter curves, and resemblances between the vernal and autumnal 

 curves. 



Tliese results, together with a certain degree of opposition be- 

 tween the hniar curves of rainfall and temperature, seemed to 

 indicate a partial dependence of the temperature upon the tidal 

 currents in the atmosphere. If this hypothe.-is was correct, it 

 seemed probable that some of the planets, especially Jupiter, 

 shouhl furnish corroborative indications. The observations, both 

 of rainfall and of temperature, were therefore arran^^ed succes- 

 sively in accordance with the positions of Jupiter, Venus, Nep- 

 tune, and Mercury. The arrani^eujent resulteil in the production 

 of consistent curves, varying with the varying distances of the 

 several planets, and with their positions relative to the sun. In 

 comjjaring these curves an opposition was apparent between those 

 of rainfall and temperature, which was more strongly marked 

 than that which had been previously noticed in the lunar curves. 

 It seems unreasonable to attribute the temperature fluctuations to 

 varying planetary radiation ; but it is. easy to understand that any 

 influence which tends so to disturb the atmosphere as to produce 

 a northcrl}' wind, should depress the temjierature and increase 

 precipitation, while one which tends to produce a south wind, in- 

 creases both the temperature and the evajioration. 



THE TRANSITS OF VENUS. 



The French Astronomer Royal is wisely making arrangements 

 in good time for ol)serving the transits of Venus, which will take 

 place in the year 1874 and 1882. The event is one of considerable 

 interest and value to scientifle men, and it is therefore desirable 

 that it should be viewed from those parts of the earth's surface 

 where it can be best ol)served. The stations flxed upon Un' 1874 

 are Oahu (one of the Sandwich islands), Kerguelen Island (in tiie 

 Indian Ocean), Rodriguez (adeijendeucy of the Mauritius), Auck- 

 land (New Zealand), and Alexandria. Both the Admiralty and 

 the Treasury have responded with alacrity to the appeal which 

 has been made to them for funds. Mr. Warren De la Rue is of 

 opinion that photograph}' may be used witli the utmost advantage 

 in registering the transit. 



DR. TYNDALL's theory OF COMETS. 



Prof. Tyndall has developed a cometary theory out of his late 

 researches upon the actinic power of light. It will be remem- 

 bered that he has ibund that a beam of liglit is capable of forming 

 a bright glowing cloud in its course through a space containing a 

 modicum of vapor, the; said cloud being lirst reduced by the chemi- 

 cal action of the light, and then rendered visible by illumination 

 of the con(k'.nse<| ]);ii-ticles. 



The application of this i)rincij)le to the explanation of cometary 

 pheuomcua is as follows : A comet is held to be a mass of vapor 



