¢ 
1864. | Astronomy. 449 
and minimum solar spot frequency. By means of these hypotheses, 
our author explains many of the phenomena of the solar spots, the 
magnetic variations, the alterations of terrestrial temperature, and the 
changes in the direction of the wind. He has calculated that the 
greatest and least values of the sidereal period of revolution of the 
ring will be 29-12 and 22-08 days respectively. From these numbers 
we find that the greatest distance of the ring from the sun is 0185, 
the radius of the earth’s orbit being taken as unity ; the least distance 
0-154, and the mean 0:169. Taking Mr. Hind’s value of the mean 
distance of the earth from the sun, namely, 91,328,600 miles, we 
have— 
Greatest distance of the rmg=16,921,000 miles; 
Least a a =14,068,000 ,, 
Mean 43 i =15,494,500 ,, 
and the range of movement to and fro, in a radial direction, 
= 2,853,000 miles. The greatest attractive force of the sun on the 
ring being taken as unity, the least will be 0691. Should future 
researches place the existence of this ring beyond doubt, this will, it 
is believed, be the first instance in which the conclusions of physical 
astronomy have been confirmed by the results of an investigation of 
magnetical and meteorological phenomena. 
M. Faye* has given an account of a new method proposed by 
M. De Littrow, for determining the time and the longitude at sea. 
The method consists in the determination of the time by two circum- 
meridional observations of the sun, preserving at the same time 
the observation of the true noon for the latitude. The two altitudes 
may be taken at pleasure, on the same side, or on opposite sides of 
the meridian ; the interval of time is arbitrary, varying according to 
the circumstances, from 5 to 80 or 40 minutes ; and as the calculation 
takes only five minutes, the navigator may in half-an-hour take his 
observations, and effect all the calculations necessary for finding at 
once the longitude and the latitude. The new process depends on the 
fact that when, as at sea, a scrupulous accuracy is not required, 
the circummeridional altitudes of the sun may be used for deter- 
mining the time. The method was tried on the voyage of circum- 
navigation of the Austrian frigate, the ‘ Novara,’ and the results were 
generally correct, within a probable error of one or two nautical miles. 
This method might be equally useful on terra firma as at sea; for 
travellers, as well as for sailors, it would be useful to have a convenient 
method of determining daily their latitude and longitude, by observa- 
tions concentrated at a single epoch of the day—about noon. 
Tur Royat ASTRONOMICAL SocIETyY. 
In the ‘Proceedings of the Royal Astronomical Society,’ for 
March, Mr. Dunkin has given an interesting note on the number of 
luminous particles contained within a confined space on the sun’s 
dise. The power used was about 100, and a system of wires in the 
* «Comptes Rendus,’ March 7, 1864. 
