SCIENTIFIC SUMMARY. 
357 
fore the water is flowing from both sides towards B and towards F. At D 
and H the water is sinking most rapidly ; therefore the water is receding 
on both sides from D and from H. Hence it follows that the directions of 
currents are represented by the arrows in the diagram. 
“ We have now obtained complete knowledge of the state of the currents in 
the strong-line ellipse, and from these we can infer the state of the currents 
in the dotted line, or subsequent ellipse, remarking that in this subsequent 
case the subsequent ellipse, which in the preceding case the preceding currents 
held to the axes of the preceding ellipse. And, by comparing these, we shall 
learn what are the changes made in the currents at each place, and what must 
be the forces which produce these changes. 
O 
u At A, C, E, G, the current is scarcely changed, or the forces are 0. At B 
a current 0 is changed to \ and a current ^ is changed to 0, or the force 
is . At D a current 0 is changed to j, and a current / is changed 
to 0, or the force is j. In like manner, at F, the force is \ ; and at H 
the force is f 1 . These forces are such as are produced by the moon in the 
position shown in the diagram ^ in the opposite position, and in no other 
position. Therefore it is low water under the moon.” 
Father Secchi has published an interesting memoir on Sim Spots, and in 
some well-arranged experiments has found a decided difference in the intensity, 
and some difference in the colour, of sun light proceeding from the centre and 
limb of the sun. 
We have the visitation of two observatories to chronicle, — those of Greenwich 
and Glasgow. The former took place on June 2 ; the latter on March 29. 
Mr. Airy’s address this year is of less interest than usual. In an address to 
the “ individual members” of the Board of Visitors, Mr. Airy gives an 
account of the boring of the cube of the transit instrument to allow of the 
examination of collimator by collimator without raising the instrument. The 
Admiralty have consented to the purchase of two 7-inch collimators in place 
of the present smaller ones. Mr. Airy has observed the sun with the great 
equatorial, and Mr. Stone has used the same instrument for a prismatic 
