Chemistry and Physics. 457 
of elementary dynamical principles.— Nature, xiv, 452. _E. © 
13. Protection of Buildings from Lightning.—Prot. Maxwkt 
popes another system of protecting buildings quite unlike that 
Samat nave Attention is generally especially devoted to the 
ae : of the conductor, to secure an elevated and pointed ter- 
nal above and a good connection with moist earth below. This 
dis i iff 
discharge cannot occur between two bodies unless the difference 
aml by good conductors as wire ropes. 
the 1 the exterior is covered with a good conductor. Thus, if 
roof, walls ana ground floor are covered with thick sheet- 
“hil no electrical effect could be produced inside by a thunder 
0 N and the building 
hot necessary to take ~~ to facilitate 
ature, xiv, 479. 
Larth.—Mr. Jamzs Crout, L1.D., F.R.S., of the Geological Survey, 
ey a paper “ On the Tidal Retardation Argument fo the Age 
of the Earth.” Many years Si illiam Thomson demon- 
- physical considerations that the views' which then 
Prevailed in regard to geological time @ the age of our globe 
were perfectly erroneous. main @ ents, as are well 
ible age; and 
known, were—first, that based on the sun’s possibl 
condly, that based on the secular cooling of the earth. More 
t (Trans. Geol. Soc of 
k §0 sips Bh .d on tidal retardation. It is well 
i that owing to tidal retardation the rate f 
®n is slowly diminishing, and it is, therefore, evident that if we 
