226 Scientific Intelligence. 
closely the phthalein of phenol; the other a red coloring matter, 
an isomer of alizarin—to which Grimm gives the name quinizarin 
C,,H,O,. It is produced according to the equation: 
C,H,0,+C,H,0,=C,,H,O,+H,0. 
quinizarin to a deep blue color. Since anthracene results when its 
vapor is passed over heated zinc dust, Grimm suggests its close 
similarity with alizarin, and proposes for it the rational formula 
. —--CO-.-- 
C,H, 10_.-CeH2(OH),. 
Ree B 
— Ber, Berl. Chem. Ges., vi, 506, 1873. G. F. B. 
5 v@ Horizontal Pendulum.—Z ER describes a series of 
‘25 of a second. The springs were about eight inches long and 
the delicacy of the instrument was such that its vibrations were 
easily observed when the time was increased to thirty seconds, 
corresponding to a diminution of the force of gravity of fourteeD 
thousand times. In the actual experiments a time of vibration of 
