Vol. XXV. No. 10.] 
POPULAE SCIENCE I^EWS, 
145 
cause. It was by means of the line sand, stone, 
and blocks of locks which fell between the ice 
and rocks on which it moved that the grinding 
work of the glacier was done. These materials, 
held by the ice as it crept along, were pressed 
against the sides of the rock and the bottom of 
the valley so firmly and persistently as to descend 
into each little hollow and mount over each ridge, 
yet moving all the while steadily in one dominant 
direction with the general movement of the gla- 
cier. As a result, the most compact resisting 
rocks are ground down, smoothed, polished, and 
straited. Where they liave been long exposeil 
this peculiar suiface is apt to be ettaced by the 
disintegrating action of the weather, though it 
retains its hold with extraordinary pertinacity. 
Observations of the directions of the striic have 
shown that, on the whole, these markings diverge 
from thi' main masses of high ground. In Scan- 
dinavia they run westward and southward on the 
Norwegian coast, and eastwai-d or southeastward 
across the lower grounds of Sweden. When the 
ice descended into the basin of the Baltic and the 
plains of Xorthern Germany it moved southward 
and southeastward, but seems to have slightly 
changed iis direction in difl'ereut areas and at dif- 
ferent times. Its movement can be traced partly 
from the striiP on the soil, but more generally 
f rotn the glacial drift it left behind ; thus it can 
be sliowu to have moved down the Baltic into the 
Xorth Sea. .\t Berlin its movement must have 
been from east to west : but at Leipsic, as recently 
ascertained by Credner, it came from N. X. W. to 
S. S. E., being doubtless shed oft' in that direction 
by the high grounds of the Hartz Mountains. Its 
southern limits can be traced with tolerable clear- 
ness from Jevennar in lliilland eastward across 
the Hhiiie Valley, along the base of the Westpha- 
lian hills, round the projecting promontory of the 
Hartz, and then southward through Saxony to 
the roots of the Erzgebirge. Passing next south- 
eastward along the flanks of the Kusen and Sude- 
ten range, it sweeps across l'<dand into Russia, 
circling around by Kief, and northward by Xijni 
Xovgorod toward the Urals. It was estimated 
that, including Finland, Scandinavia, and the 
Uritish Isles, the ice must have covered no less 
than 1,700,000 square kilometers of the present 
low lands of Europe. 
The glaciers, as indicated above, act in two 
ways: First, by the removal of pieces of rock; 
and then by rubbing, rounding, smoothing, and 
grooving the roclxs and stones <)V(m- and u])<(n 
which the masses of ice move. If the glaci<'r ti-r- 
minates on dry land, the blocks of stone it canies 
with it are only transported as far as the ground: 
lint it it terminates in the sea or in a lake, blocks 
of the ice are broken oft' and float with this load 
of rocks wherever wind and tide may drive them, 
until the warmth of the water, the air, and the 
sun will have completely thawed them, when the 
rocks sink to the bottom. This and other ques- 
tions regarding glaciers will be treated more fully 
at another time. 
[Microscopical Journal.] 
A UXIVERSAL STAND. 
BV A. G. FIELD, M. U. 
Fig. 1 below represents a stand adapted to the 
wants of the professional or amateur who uses the 
microscope and cameja. It consists of base A, 
14X14X5 inches, to which is seemed, by dovetail, 
glue, and screws, two uprights, 15, B, 5X1 inches, 
one three and the other seven feet in height. These 
are precisely p<Tpi'ndicular to base, to bring in- 
struments and oly.'ct in line when centered. They 
are grooved on edges to receive tongues or arms, 
C, C, C, C, of the secondary base D, and also on 
the camera-carrier H. The uprights are made 
ttrmer by additional pieces extending up thirty 
inches from the base. The secondary liase, 14 X 
14 inches, is corner-braced as shown, and is ad- 
justable as to height, being secured in desired 
position by set-screw E. in the center is a hole. 
Fig. 1. 
one and a half inches in diameter, which receives 
the tube of the mic oseope when it is placed on 
the base for high amplilication in photo-microg- 
raphy, and also the gu !geon of the support of the 
base-board O when used in copying oi- photogra- 
phy. G is a lamp-rest which slides on cleats .il- 
taehed to the corner braces, and has an upright 
for concave reflector when desired. II, sliding 
carrier for camera, with tongued arn)s of sulH- 
cient width to bring the photographic lens collar 
precisely over the microscopic tube when centered 
Fig. 2. 
on either base. I, set-screw to retain it in posi- 
tion, and J, milled head of pinion by which it is 
racked down to attach camera, K, to eye-piece of 
microscope. This light-tight connection is made 
with one-half of child's rubber ball, perforated in 
centei- to rtt neck of eye-piece, and of surticieut 
size to till the collar of Ihe photogiaphic lens. 
Pig. 2 illustrates the use of the stand in copy- 
ing, enlarging, and reducing, and requires but lit- 
tle explanation. X, X, base-board, 5X1 inches, 
four feet long, groovi^d on edges to r<>ceive tongues 
on arms of camera-carrier. It is hit ged to apex 
of wedge-shaped block, O, the gudgeon of which 
fits snugly into the hole in center of supplemental 
base. S, telescopic boxes. R, R, slat passing 
beneath the camera-carrier, with upright, t^, for 
carrying the picture to be copied, the distance 
respectively between the lens and picture, and 
lens and ground glass, being regulated by the 
operator without leaving his position at the focus- 
ing screen, so that all copies may be brought to a 
uniform size, as tor lantern-slides, w ithout regard 
to the size of the original. Removing the tele- 
scopic boxes and slat, we have a conveident cam- 
era-stand for inside use, the lateral movements 
being secured by the gudgeon attachment, and 
the vertical by the screw-brace P. 
If used ordinarily as a microscope-stand, the 
instruments are always in line and position for 
photo-micrography. 
A NOVEL CURRENT-BREAKER. 
It frequently happens that electric lights or 
other electrical apparatus are placed in powder 
magazines, flour mills, or storehouses of ii.-iphtha 
or other inflammable or explosive substances. In 
turning the current on or oft", sjiarks are liable to 
pass between the ends of the wires, which, under 
favorable circumstances, might cause a disastrous 
explosion. 
The current-breaker here illustrated is so ar- 
ranged that the rupture of the circuit and the 
passage of the spark take place in an air-tight 
rubber bulb, and its construction is rendered suf- 
Hciently clear by the engraving. The insulated 
wires forming the electrical circuit are inclosed in 
a flexible tube, to one end of which is attached a 
rubber bulb half tilled with mercury. The ends 
of the wires, from which the insulating covering 
is removed, are sealed into the lower end of the 
bulb. When the tube is bent upwards in the posi- 
tion B or C, the mercury surrounds the wires, 
completing the electric circuit and allowing the 
current to pass. To break the circuit it is only 
necessary to unhook the end of the tube and 
allow it to hang straight down in the position A 
or D. The current is at once broken, and any 
spark that may pass between the wires is com- 
pletely cut oft" from the outside air and rendered 
harmless. 
