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have obtained straw from wheat so grown, and have found, after it has been 
treated with nitric acid, and the silicious remains placed on the field of the 
microscope, that it consisted wholly of the silicious shields of Diatomacese, 
the same as found in the infusorial earth, excepting that the larger discs in 
their perfect form were absent ( Actinocyclus Ehrenbergii and Actinoptychus 
undulatus). My conclusions are that they — and there probably may be other 
forms — are too large to enter the root capillaries. During the coming summer 
I will attempt, if possible, to make micrometer measurements of both. The 
discovery of Diatomacese in their original form in this wheat-straw precludes 
the possibility of the infusorial earth having undergone any chemical change 
in the soil, either by forming chemical combination with the alkalies or the 
earths, or by suffering physical disintegration from any catalytic action of 
any salts present in the soil. In the particles of silica placed upon the glass 
slide, when they were completely separated from each other, the outlines of 
the individual diatoms were sharply and distinctly defined. On the other 
hand, when the physical action of ebullition with nitric acid was not suffi- 
cient for the complete separation of the particles of the epidermal shield, 
there was observed a marvellous interlacing of the various forms, showing 
that they were conveyed by the sap-cells directly to the section of the plant 
where they were destined to complete its structure. I have examined 
several specimens of straw, taken at random in the market ; the silica in 
each specimen consisted of plates, very thin, and truncated at the comers.” 
Musical Sand Examined beneath the Microscope. — A paper on this subject, 
which is really a somewhat curious one, is published in the last number of 
the u Proceedings of the California Academy of Sciences ” (vol. v). He states 
that “ in order to ascertain, if possible, the cause of the sound that is pro- 
duced by the sand from Kauai, presented to the Academy at a former meet- 
ing, I investigated its structure under the microscope, and I think the facts 
I have ascertained fully explain the manner in which the sound is produced. 
As the grains of sand, although small, are quite opaque, it was necessary to 
prepare them so that they should be sufficiently transparent to render their 
structure visible. This was effected by fastening them to a glass slide .and 
grinding them down until one flat surface was obtained. This surface was 
then attached to another slide, and the original slide being removed, the 
sand was again ground down until sufficiently transparent. The grains 
were found to be chiefly composed of small portions of coral and apparently 
calcareous sponges, and presented under the microscope a most interesting 
object. They were all more or less perforated with small holes, in some 
instances forming tubes, but mostly terminating in blind cavities, which 
were frequently enlarged in the interior of the grains, communicating with 
the surface by a small opening. A few Foraminiferae were also met with, 
and two or three specimens of what appeared to be a minute bivalve shell. 
Besides these elements, evidently derived from living beings, the sand con- 
tained small black particles, which the microscope showed to be formed 
principally of crystals of augite, nepheline, and magnetic oxide of iron, im- 
bedded in a glassy matrix. These were undoubtedly volcanic sands. The 
structure of these grains fully, I think, explains the reason why sound is 
emitted when they are set in motion. The friction against each other causes 
vibrations in their substance, and consequently in the sides of the cavities 
