148 



Mr. J. N. Lockyer. 



[Nov. 17, 



Bnstatite Mg0 3 Si = Si0 3 60, MgO 40. 

 Bronzite = Enstatite, in which, some Mg 



is replaced by Fe. 

 Nickel-iron, manganese. 

 Troilite. 



Chromite = iron protoxide 32, chromium 

 sesquioxide 68, 4- Al and Mg. 



Angite = pyroxene, Si0 2 55, CaO 23, 

 MgO 16, MnO 0-5, FeO 4. 



Silicate of calcinm, sodium, and alumi- 

 nium. 



(ft) Carbonaceous .... Carbon in combination with H and 0. 



Sulphates of Mg, Ca, Na, and K. 



Non- chondritic — 



Anorthite. 



Enstatite. 



Bronzite. 



Olivine. 



Augite. 



Troilite. 



I. The Numbers of Meteorites in Space. 



It is well known that observations of falling-stars have been used to 

 determine roughly the average number of meteorites which fall on the 

 earth each twenty-four hours ; and having this datum to determine 

 the average distance apart between the meteorites in those parts of 

 space which are traversed by the earth as a member of the solar 

 system, Dr. Schmidt, of Athens, from observations made during 

 seventeen years, found that the mean hourly number of luminous 

 meteors visible on a clear moonless night by one observer was four- 

 teen, taking the time of observation from midnight to 1 a.m. 



It has been further experimentally shown that a large group of 

 observers who might include the whole hemisphere in their observa- 

 tions would see about six times as many as are visible to one eye. 

 Professor H. A. Newton and others have calculated that making all 

 proper corrections the n amber which might be visible over the whole 

 earth would be a little greater than 10,000 times as many as could 

 be seen at one place. From this we gather that not less than twenty 

 millions of luminous meteors fall upon our planet daily, each of which 

 in a dark clear night would present us with the well-known pheno- 

 menon of a shooting star. 



This number, however, by no means represents the total number of 

 minute meteorites that enter our atmosphere, because many entirely 

 invisible to the naked eye are often seen in telescopes. It has been 

 suggested that the number of meteorites if these were included would 



