Von Hoffon the Origin of Meteoric Stones. 



supposing them to be derived from the moon must come from 

 a region lying near the centre of that side of the moon turned to- 

 wards us, therefore from a limited space, in which one single kind 

 of rock may predominate ; and that it is on this account the ma- 

 jority of the meteoric stones hitherto found consist of a very si- 

 milar mineralogical compound ; that, on the contrary, those from 

 a district considerably removed from the centre of the side of the 

 moon next us, and therefore belonging to a different rock forma- 

 tion, do not proceed in a direct line towards the earth, hence reach 

 us more rarely ; and that it is for this reason we find so few me- 

 teoric stones differing in their characters from the majority. We 

 must not, however, leave unnoticed the following consideration. 

 The greatest support of the lunar hypothesis is undoubtedly the 

 mathematically demonstrated possibility of bodies being projected 

 from the moon to a region within the range of attraction of the 

 earth. But the calculation by which this is proved is formed on 

 the supposition that the earth and moon remain stationary. This, 

 however, is not the case ; and the movement of the moon round 

 the earth and round the sun is communicated to the masses 

 ejected by the first. Hence these will describe an elliptical path 

 round the earth, in which they can reach the earth itself only in 

 that case when their perigeum touches the earth, or at least its 

 atmosphere. As this, however, can, in all probability, be the 

 case with only a small portion, only very few of the masses eject- 

 ed by the moon reach the earth. But as the occurrence of me- 

 teoric stones is so common, the moon, if it is their place of ori- 

 gin, must gradually lose much of its mass.* 



It is not to be denied, that, notwithstanding this last observa- 

 tion, all the circumstances mentioned in the preceding remarks 

 favour the hypothesis that meteoric stones, and the masses of na- 

 tive iron which fall from the air, can be derived from the moon. 

 But, in order to judge if it be necessary to ascribe to the moon 

 alone the origin of these masses, and to reject every other view 

 of their origin, we must examine more attentively the circum- 

 stances which, among those employed to support the opinion, 

 are still hypothetical. In this light I consider the following : 



Iron, says the hypothesis, can occur in a native state only in 

 the moon, since it is not oxidised there, owing to the moon pos- 

 * Vide Olbers in " Van ZacVs Momtliche Correspondent," vol. vii. p. 159. 



