1882 .] Correspondence. 621 
taller than their mothers. Better exercise, better dress, and per- 
haps better food and air, might lead us to expedt an increase in 
the height of our tennis-playing generation of girls, but I fancy 
it is more than would be expedted — perhaps quite half an inch. 
Is this the first stage in the development of the late Lord Lytton’s 
“ Coming Race ” ? — I am, &c., 
Hugh Browns. 
Nottingham, September 20, 1882. 
INTELLIGENCE IN A HORSE. 
To the Editor of the Journal of Science. 
Sir,— The following incident may be interesting to some of your 
readers. It is well known that horses in some parts of South 
Africa are much annoyed by a kind of tick, which sucks their 
blood till it swells out to the size of a large pea. A charger 
named Joe, belonging to the Colonial cavalry stationed at Maseru 
during the Basut ) War, if thus attacked whilst pasturing would 
canter to the fort, seek out his rider, and express by signs what 
was the matter. The trooper would seek out the tick, crush it, 
and throw it on the ground. The horse has then, on more than 
one occasion, examined the remains of its enemy, and given 
them a blow with his fore-hoof, as if to make “ assurance doubly 
sure/’ — I am, &c., 
E. A. S. 
OBJECTS SEEN THROUGH BLUE GLASS. 
To the Editor of the Journal of Science . 
Sir, — The glass used byyourcorrespondent (“ Journal of Science,” 
September, 1882, p. 562) was in all probability the ordinary blue 
glass coloured with coba t : this if examined with the spedtro- 
scope will be found, according to its depth of tint, to transmit 
more or less red light, which would account for some of the tints 
observed. The effedl is easily seen in the lights of some tram- 
cars which are coloured blue ; in addition to the blue tint of the 
glass, a strong red colour may be observed about the light. I 
will examine the glass used if your correspondent wishes it. — 
I am, &c., 
W. T, Suffolk, 
