442 
POPULAR SCIENCE REVIEW. 
large number of measurements of crystals of Atacamite, from Wallarro, 
South Australia. These prove that the species is, as hitherto supposed, 
orthorhombic, but show further some irregularities in the planes of the 
vertical series, which can be explained only by the assumption of a dome 
40-i taking the place of i-i, and a corresponding pyramid, in place of the 
prism I. The crystals under examination were placed in the hands of the 
author by Dr. A. Schrauf, of the Vienna Mineralogical Museum. 
Living stonite, a New Mineral. — Mr. Marianus Barcena describes this in 
“El Minero Mexicado,” May 1874. He says that Livingstonite much 
resembles in colour and aspect stibnite or sulphide of antimony. It occurs- 
in prisms, apparently isomorphous with stibnite, and like it in thin columnar 
groups. Color, bright lead-gray ; of powder red, instead of black like 
stibnite. Hardness, 2 on Breithaupt’s scale. Density, at 16° C, 4-81. 
Puses at the first touch of the blowpipe flame, and gives out abundant 
white fumes. Cold nitric acid does not sensibly attack it; but warm 
dissolves it, and a white residuum falls. Sulphydric acid precipitates it, 
forming a yellow sulphide and another of a black colour. Reactions show 
that it contains mercury as well as antimony. An analysis has not yet been 
completed, but au assay proved the presence of 10 per cent, of mercury, 
showing that it is in all probability a sulphide of mercury and antimony. It 
is from Huitzuco, in the State of Guerrero, Mexico. Mr. Barcena has named 
it in honour of the distinguished African traveller, Dr. Livingstone. 
MICROSCOPY. 
A Finder for Llartnack's Microscopes. — The following is from u Science- 
Gossip” for September: — Those of our readers who use Hartnack’s, or 
microscopes of similar construction, will find Mr. Hicks’s contrivance for the 
purpose of easily refinding an object at any time very useful. A line is to be 
ruled across the centre of the stage from side to side. Crossing this line at 
right angles are ruled two lines about two inches apart, one on either side 
of the aperture of the stage. In order to use the finder, a label about half 
an inch in diameter is fixed to each end of the slide, the lines on the stage- 
left uncovered being used as guides for continuing the lines across the label 
with a pencil-mark. If the lines marked on the label be made to coincide 
with those on the stage, the object on the slide will be found in the centre 
of the field. Mr. Hicks says that he finds roughing the ends of the slide 
with a corundum file, and marking the point of intersection with an ink dot, 
preferable to the labels, as being more accurate. "We think a label some- 
what less than an inch square (about nine-tenths of an inch), so as the stage- 
lines might be seen round the margins, would be more advantageous than 
those of a circular form, as the position of the stage-lines could be marked 
on the margin of the label, and the position of the object might be registered 
by marking down the number of dots from the top left-hand corner ; sup- 
posing it to be the fourth in a vertical and the seventh in a horizontal direc- 
tion, it could be registered either 4 | or 7 — . 
Microscopy of the Quarter . — The following papers, some of which are of 
