30 OOo O RAPORT—TS858. °° °° 7 
bine to render mere estimations of magnitude worthless for determining the period 
of a variable star. It is therefore best to select a number of comparison stars; 
ranging in magnitude from the maximum brightness of the variable, to the minimum 
visibile of the telescope, and if possible in the same field of view, to assume the 
mean of several estimations of these comparison stars, made on different nights, as 
correct, and so to note the difference of magnitude between the variable and such 
of the comparison stars as most nearly agree with it in brilliancy. By this means 
small variations which must otherwise escape notice may be satisfactorily detected, 
and a change amounting to a whole magnitude cannot possibly be overlooked. The 
following observations of the new variable star were by this means obtained :— 
1858, July 3 ...... 8°2 magnitude. . August 1...... 9°4 magnitude. 
» Ll «sve 8°0 by »» 8 sseece 9°6 » 
xs 19 seers 90 >» of BD vaewae DD } 
99 29 seers O'S ” Sept 5 esses 11°4 9s 
Combining these with Professor Argelander’s in 1849, and with my own records of 
invisibility in 1856, it appears most probable that seven maxima occurred between 
August 7th, 1849, and July 3rd, 1858 ; in which case the period will not differ much 
from 465 days, and the next maximum will fall due in September or October 1859. 
It would, however, be premature to state this as anything more than a probable 
surmise, only to be decided by further observation. 
-On the Constitution of Comets. By Dr. F. A. Strsestrém, of Stockholm. 
- The prevailing opinion about the comets is, I think, that these heavenly bodies are 
most likely to consist of an infinitely thin gas, or perhaps rather dust. I have tried 
to show the great difficulty of explaining the diaphaneity of the comet, unless the so- 
called ‘dust’? is composed of more or less considerable masses of some dense 
(planetary) matter (the comets might be agglomerations of bodies like the metoric 
stones). Under this supposition, the diaphaneity of the comets may be experi- 
mentally represented by an ordinary rotatory machine (used to show the figure of 
the earth as being an effect of her rotation), which, if the brass rings have been 
covered with white paper, wil! show a globe of feeble white, through which a candle- 
light may be seen with undiminished intensity. [In this experiment the rotation 
may be considered only as having the same optical effect as in reality the great 
distance. 
All a other phenomena, such as the great variation in the light, intensity, the 
changes of volume, &c., seem to be very easily explained in this hypothesis. As to 
the ¢ail of the comet, I have tried to show that it may be not unsatisfactorily ex- 
plained by a ring (also consisting of the above-named smail bodies of dense matter). 
surrounding the bulk of the comet; and indeed the comet of 1813 presented an 
appearance almost like an experimentum crucis for this hypothesis. However, 
further observations are necessary to establish any theory in this belief. 
On the successful establishment, by Astronomer Broun, of a Meteorological 
and Magnetical Observatory at Travancore, at 6200 feet above the Level 
of the Sea; with Results of Magnetical Observations at Trevandrum, as 
communicated in a Letter from Mr. Broun to General Sir Thomas Bris- 
bane. By Colonel Syxes, F.RS. 
The author,—after giving a graphic account of the wild and difficult country in 
which Mr. Broun, now Astronomer to the Rajah of Travancore, formerly assistant 
to Sir T. Brisbane, and the dangers he had to encounter from wild beasts as well as 
the difficulty of inducing the necessary workmen and labourers to encounter the cold 
as well as the dangers of these elevated regions, having many nights to sleep ex- 
posed to the weather and to heavy rains while the observatory was constructing, 
read the following letter:— 
