458 Scientific Intelligence. 
ber of sun-spots. Three such maxima occurred in 1849, 1860 and 
1872, and regarding each as extending over three years, the num- 
ber of cyclones is 26, 39 and 36, while in the corresponding minima 
of 1856 and 1867, the number is only 13 and 21. 24 hurricanes 
were also recorded in Mauritius between 1731 and 1850, of which 
17 occurred during maxima, and seven only during minima sun- 
spot periods. 
The examination of 93 tables of rainfall renders probable a sim- 
ilar periodicity in this respect also.— Nature, Oct. 9th. E. c. P 
protect the subjacent layers. 
A couple thus prepared, with sheets of lead half a meter square, 
after being charged with two Bunsen cells, will heat to redness 
or twenty minutes a platinum wire half a millimeter in diameter 
and a wire a fifth of a millimeter in diameter for an hour, without 
any communication with the primary source, and even forty-eight 
hours after it has been charged. 
will heat a platinum wire so that a gas burner may be lit a hun- 
dred times without rech rging, and with a larger battery three or 
four thousand consecutive illuminations have been obtained. y 
may also be associated with electric bells so as to work with the 
