258 



natore 



[November 5, 1914 



Coming now to the method of making- observa- 

 tions and the observations themselves, a word of 

 warning should be given to those who are not 

 famiHar with making solar observations. No one 

 should use a pair of binoculars or a telescope of 

 any size unless proper precautions are taken ; 

 otherwise the loss of eyesight may be the result. 

 It is better to make no attempt to watch the 

 transit than to make risky observations. Proper 

 dark glasses should be secured beforehand, and 

 fixed firmly in position so that they cannot fall 

 off at the critical time. A method devoid of all 

 risk is to throw the solar image on a screen ; in 

 this way more than one observer can watch the 

 transit. 



In the Comptes rendus of the Paris Academy 

 of Sciences for October 5 Monsieur Bigourdan 

 summarises a series of the principal precautions 

 which should be taken by those who wish to make 

 useful observations. Such precautions are neces- 

 sary because a transit of Mercury seems to be 

 accompanied by various appearances the causes of 

 which are not always well known. It is there- 

 fore advisable to eliminate so far as possible all 

 possible errors which may arise through instru- 

 mental deficiencies. 



He suggests first of all the method of observing 

 the sun directly, and not by projection, for in the 

 latter case delicate details are chiefly lost. To 

 diminish the solar light he proposes a method of 

 semi-silvering the outer surface of the objective, 

 but he adds that this method holds good only 

 when the sky is clear, otherwise observation 

 would be impossible. The practical method of 

 employing graduated and compensated dark 

 glasses is chiefly recommended, and the greatest 

 aperture of the telescope should be employed, 

 having due regard to tlie heating at the focus, 

 and the resulting cracking of the graduated 

 glass. 



While giving the preference to telescopes of 

 large aperture, the results furnished by moderate 

 or even small telescopes should not be neglected. 

 Both reflectors and refractors should be brought 

 into use. He directs attention to the importance 

 of having diaphragms well blackened and sup- 

 pressing for the time being any fixed accessories in 

 telescopes which ordinarily serve for the illumina- 

 tion of the field, and which, situated in the path 

 of the beam or in the vicinity of it would produce 

 hurtful reflections. When an instrument can be 

 reversed or can take up two positions successively 

 to the right and left of its mounting, it should be 

 utilised alternately in these positions, thus turning 

 the whole optical system through i8o°. Finally, 

 he points out the importance of observing every 

 appearance, however abnormal, by studying it in 

 different positions of the telescope, with different 

 eyepieces; dark glasses, etc. While the above 

 precautions are particularly to be recommended 

 for accurate observations, others of a secondary 

 nature must not be forgotten. 



With regard to the observations to be made 

 during the planet's transit, those of first import- 

 ance are the determinations of the accurate time 



NO. 2349, VOL. 94] 



of the internal and external contacts. Next come 

 the measurements for the determination of the 

 diameter and the flattening of the planet's disc. 

 Rings (aureoles) around the black disc of Mercury 

 form interesting objects for observation, and their 

 intensity in relation to the neighbouring solar 

 surface should be studied. 



A spectroscopic survey of these rings would 

 decide whether their existence was real or not^ 

 and the question of an atmosphere round Mercury 

 could thus possibly be inquired into. Other points 

 of interest relate to luminous appearances on the 

 dark disc of the planet, possibility of satellites, 

 occultations of solar spots, and faculae by the 

 disc, etc. 



Successful observations of these and other 

 phenomena help to further our knowledge of the 

 movements and physical constitution of this the 

 smallest of the planets. 



A METEORITIC FALL IN LANCASHIRE 



ON Tuesday evening, October 13, at 8.45, the 

 inhabitants of Lancashire and Cheshire were 

 alarmed by a sudden and vivid illumination of the 

 heavens caused by a ball of fire moving slowly 

 from about S.S.E. to N.N.W. It lit up the whole 

 countryside and consisted of several outbursts, the 

 final one being the brightest flash. Then a short 

 interval afterwards, the estimated periods varying 

 from a few seconds to four minutes, according to 

 the distances of the observers, there was a tre- 

 mendous report, as though a thunder-like ex- 

 plosion had occurred in the region a few miles 

 west of Wigan. 



This was followed by a series of rumblings 

 extending apparently back along the flight of the 

 luminous object. At several places the windows 

 are stated to have been shaken, and the vibration 

 was such that it presented some similarity to an 

 earthquake shock. 



Numbers of persons in Manchester, Liverpool, 

 Halifax, Northwich, Bolton, Macclesfield, and 

 other towns witnessed the event and heard the 

 noise, and in the present agitated state of the 

 public mind, all sorts of ideas were formed as to 

 the nature of the phenomenon. 



A large detonating meteor had, notwithstanding 

 the rather cloudy state of the atmosphere, not only 

 penetrated the lower region of the air, but had 

 resisted complete disruption and fallen to the 

 ground. It was discovered on the following day 

 at Appley Bridge, four miles W.N.W\ of Wigan. 

 An employee of Mr. Lyon of Halliwell Farm 

 noticed a newly turned up mound in a field and. 

 on examination, he saw a reddish mass of strange 

 material lying in a hole about 18 in. below the 

 surface. On being dug out the object weighed 

 about 33 lbs. ^nd in appearance looked like a 

 rough piece of burnt iron. Subsequently, the 

 county police took possession of the strange 

 visitor, and it has since been handed over to the 

 curator of the Godlee Observatory, Manchester, 

 for proper investigation. 



