NOTES AND QUERIES. 109g 
FisH ScaLtes.—Mr. Charles Collins, nephew of the well-known 
microscope maker of the same name, has just issued a series of 
these interesting objects, comprising 48 distinct species. 
As Opaque slides the scales are splendid objects for the Monocu- 
lar as well as Binocular, and the skins, though from the same 
fishes, will be found, when examined, to warrant the repetition. 
The scales of the Eel and Perch under the VPo/artscope are 
pretty well-known, but for variety and beauty the number will 
bear adding to. 
Mr. Davies in his work on the Preparation and Mounting of 
Microscopic Objects, says, speaking of “ Fish Scales,” “ the variety 
and beauty of these are quite surprising.” 
A very interesting article upon “Fish Scales” is to be found in 
the “ Micrographic Dictionary.” The following is an extract from 
the same :— 
“ Fach scale is contained in a distinct sac of the Skin or Cutis, 
covered externally with its pigment layer and epidermis. The 
Cutis itself consists of interlacing fibres of areolar tissue with 
formative cells. The pigment layer is composed of elegant pig- 
ment-cells with long processes. Immediately above the upper 
surface of the Scales lies a very fine membrane, distinct from the 
Cutis, in which the impressions of the irregularities of surface 
existing upon the Scales are visible. 
“In some fishes, as the Eel, the Scales do not project beyond the 
surface ; hence the Eel is commonly supposed to possess no 
Scales. ‘They are easily seen, however, in a dried piece of the 
Skin, mounted in balsam, covered by the Skin with its pigment- 
cells, the whole forming a very beautiful object.” 
ATMOSPHERIC DUST.—A very useful little work was published in 
Paris in 1877 under the authorship | of M. Gaston Tissandier, under 
the title of “‘Zes Poussiéres de Pair,” and proved to be an admirable 
little dvochure treating upon the subject. The first sixteen pages is 
devoted to the description of various appliances for catching the 
dust of the air; and to ensure a quantitative method, great care 
has been taken to show how the air aspirated has been measured. 
The apparatus shown on page four fairly resembles the drum, meter 
and weight of the Alpha Gas Machine, now used for impregnating 
air with a light hydro-carbon vapour for purposes of illumination, 
and no doubt this is an excellent form of apparatus for the purpose 
under discussion. 
This study is yet in its infancy, and no doubt much has yet to. 
be discovered ; but it is stated early in the work that the quantities 
of the sediment or deposit held in suspension by the atmospheric 
currents is without doubt variable with the speed of the currents, 
with their hygrometric state, and no doubt changes even with the 
