1876.] Microscopy. 258 
It may therefore be observed that no microscope will show any more 
of the structure of an object than it is possible to see by an immersion- 
objective of a power of two hundred diameters. Helmholtz t'arrives at 
the same results by another mode, giving the smallest perceptible dis- 
tances for the middle greenish yellow light, 0.000275 mill. = 55, mill. 
—H. Hacen. - 
[We print this abstract of Professor Abbe’s curious researches, though 
not without mental reservations in regard to some of its conclusions. — 
Ep.] 
TYNDALL ASSOCIATION. — The second annual “ Science Exposition ” 
of this active society was given at the City Hall, Columbus, on the 
evenings of December 7, 8, 9, and 10, 1875. A prominent part of the 
exhibition was the microscopy, in charge of the president of the micro- 
scopical ‘section of the society, Rev. I. F. Stidham. Objects calculated 
to prove attractive to a popular assemblage were displayed upon micro- 
scopes furnished mostly by the members of the society, and an explana- 
tory lecture was delivered on the first evening by Prof. A. H. Tuttle. 
The instruments, over thirty in number, were by nearly all the familiar 
makers, the following maufacturers being those that were represented by 
more than one each: Beck, Queen, Hartnack, Grunow, Ross, Zent- 
mayer, Crouch, and Fields. 
Sonorovs SAND. — The “ musical beaches ” which occur at some points 
on the New England coast and in Georgia, as well as at the more 
famous localities in Arabia, Switzerland, the Hebrides, and the Sand- 
siig Islands, have lately been attracting much attention from micro- 
‘pists. When handfuls or larger quantities of the sand are rubbed 
together, a musical sound is produced which seems to be due to the nu- 
merous microscopic pits or cavities which abound in the grains of sand. 
These pits are especially conspicuous and interesting in the Sandwich 
Islands sand. Moisture, which would temporarily obliterate the cavities, 
prevents the sound. 
Excnances., — A photograph of any specially interesting microscopic 
object will be furnished in exchange for the use of the object from 
ee to obtain a negative. The object itself will be returned uninjured 
within one week. Address proposals to R. H. Bliven, Elmore, Ohio. — 
a nned vegetable sections in exchange for good mounted objects 
= & C108 Warren Avenue, Boston. — Slides of sonorous sand 
rp Sandwich Islands in exchange for any good mounted objects. W. 
`Y 103 Warren Avenue, Boston. 
> ag tera C. A. Baldwin has tranaierted ps coat 
N.Y. ¢ g these objects to Prof. H. A. Ward’s museum, Rochester, 
» trom which they can be obtained in future. 
- W. Queen & Co.— The changes recently noticed in this firm re- 
only to the New York house. 
“Shaped die Grenzen der Leistungsfihigkeit der Mikroskop, Monatsberichte der 
ademie, 1873, page 625. 
