440 Chronicles of Science. [July, 



Balfour Stewart, F.R.S., and B. Loewy, Esq. The object of this 

 research has been to examine the qiiestion started by one of the 

 authors of the paper, whether the behaviour of sun spots with respect 

 to increase and diminution could be referred to some extraneous influ- 

 ence. In a table given, showing the behaviour of sun spots from the 

 beginning of 1854 to the end of 1864, it is seen that different spots 

 occurring about the same time on the sun's disc, behave themselves 

 in the same manner ; so that if one spot after making its appearance 

 increases until the centre line, another will do the same ; or if one 

 spot breaks out on the left or on the right half, the other spots about 

 the same period have a tendency to break out on the same half. The 

 authors suppose that this peculiarity of behaviour of spots can only be 

 explained by reference to some influence from without, and have at- 

 tempted to answer the following questions : — Is this influence sta- 

 tionary ? or if movable, can it be traced to any of the planets of our 

 system ? 



In answer to the first question, it may be remarked that it cannot 

 be found by investigation that there is any connection between a cer- 

 tain behaviour of sun spots and a certain period of the year, and 

 hence there is no reason to suppose that the external influence is fixed. 

 In the next place does this influence, if movable", move faster or slower 

 than the earth ? If faster it will pass over the sun's disc from left to 

 right ; but if, on the other hand, the influence move more slowly than 

 the earth, it will move from right to left ; so that a tendency of spots 

 to form on the disc will be followed by a tendency to increase, not de- 

 crease after making their appearance. It is shown by a table that a 

 tendency of spots to break out is followed by a tendency of spots to 

 decrease after making their appearance, and it is thereby concluded 

 that the influence moves faster than the earth. This would seem to 

 point to either Mercury or Venus, as the agent in this matter, but the 

 behaviour varies too slowly to be caused by the former. Venus there- 

 fore appears to be the influencing agent, and a table is given which 

 seems to show that the behaviour of spots appears to be connected 

 with the position of Venus in such a manner that spots dissolve when 

 that part of the sun's surface in which they exist approaches the neigh- 

 bourhood of this planet, while on the other hand as the sun's disc 

 recedes from this planet spots begin to break out and reach their 

 maximum on the opposite side. A legitimate deduction from these 

 observations is, that the behaviour of spots is influenced by something 

 from without ; and from the nature of the spot-behaviour, the authors 

 conclude that this influence travels faster than the earth ; and finally, 

 they find that the behaviour of spots appears to be determined by the 

 position of Venus in such a manner that a spot wanes as it approaches 

 this planet by rotation, and on the other hand breaks out and in- 

 creases as it recedes from the neighbourhood of the planet, reaching 

 its maximum on the opposite side. The authors do not, however, 

 mean to convey the meaning that Venus is the cause of the ten-yearly 

 period of sun spots, but merely that there is a varying behaviour of 

 spots which appears to have reference to the position of this planet, 



