1867.) Astronomy. 523 



practical astronomy. He arranges ancient buildings into three 

 classes : — 



1st. Those which have no definite astronomical position. 

 2nd. Those which are oriented so as to have the diagonals 



of their bases towards the cardinal points. 

 3rd. Those which are oriented so as to have the sides of their 



bases towards the cardinal points. 



The diagonal method prevailed in Mesopotamia, and its most splen- 

 did example is the temple of Nebo (devoted to all the Planets) at 

 Babylon. The direct form characterizes the Pyramids. Smyth 

 finds by comparing his own measures of the Great Pyramid with 

 Sir H. Bawlinson's measures of the Nebo building, that the former, 

 though 1,500 years older, is oriented sixty times more accurately 

 than the latter. 



Major Tennant supplies a paper " On the Expansion of Brass 

 Pendula used in the Indian Trigonometrical Survey." These pendula 

 were swung in a vacuum apparatus, at a very low pressure of 

 atmosphere. There is an anomaly in the results, which would 

 appear to show that at a pressure of only 5 inches of mercury the 

 coefficient of expansion of the brass pendulum must be not only 

 increased, but is actually 13 per cent, greater than has ever before 

 been assigned to brass. It would be singular if it should appear 

 that the size -of a solid may, under certain circumstances, be subject 

 to a variation due to pressure alone. 



Messrs. De la Bue, Stewart, and Loewy discuss some recent 

 observations and remarks of Hofrath Schwabe's regarding sun-spots 

 and other solar phenomena. Schwabe notices certain phenomena 

 on the surface of the sun, which he has noticed since last December, 

 and which he remembers to have before observed, but only at the 

 time of a minimum in the number of sun-spots. The phenomena 

 are : — 1st, a total absence of faculae or faculous matter ; 2nd, the 

 absence of the usually observed scars, pores, and similar appearances ; 

 3rd, an equal brightness of the whole surface, the limb being as 

 luminous as the centre. At Schwabe's request the observations 

 made at the Kew Observatory were carefully gone over. It was 

 noticed that the phenomena occur only in years of minimum spot- 

 frequency. Schwabe is disposed to trace a connection between sun- 

 spots and meteoric showers ; and it certainly happens that the two 

 epochs at which the phenomena he describes have been presented, 

 coincided with the great shooting-star showers of 1866 and 1833. 

 It also happened that in the year 1848, which is the middle of the 

 33'25-years period there was a maximum of spots. But it does not 

 seem easy to reconcile the eleven-years spot-period with the 33£- 

 years shower-period. If there had been a steady increase of spots 

 from 1833 to 1848 and then a decrease to 1866 there would have 



