MICROSCOPY. 375 
The water of the Pontine Marshes, and of similar malarious re- 
gions, he fonnd to contain invariably, along with the common 
infusoria, a minute algoid vegetation with an abundance of trans- ` 
parent, greenish-yellow spores, qyyg mm. in diameter. This vege- 
tation develops slowly in pure water and at low temperatures, but 
rapidly in the heat of the sun and amid decomposing organic 
material. It floats upon the water, giving an iridescent film when 
young, and its spores are found in the air near the marshes, and 
even at Rome, being most abundant in warm weather and after a 
main or during a fog, and least so in a cool, dry atmosphere. Dr. 
Bolestra regards these spores as the miasmatic agent in the pro- 
duction of the intermittent fevers for which the localities are badly 
celebrated. That “ miasm,” the hitherto unknown cause of inter- 
mittent and remittent fevers, is a form of cryptogamic vegetation, 
Was urged about six years ago by Professor J. H. Salisbury, 
M.D., of Cleveland, Ohio. He published in the ‘‘ American Jour- 
nal of the Medical Sciences, in January, 1866, an elaborate paper, 
Proposing and sustaining this theory, and describing a number of 
vegetable organisms not very unlike those of M. Bolestra’s paper. 
“Eers” my Pasre.— Many young microscopists have been puz- 
zled to obtain these curious and amusing creatures which the books 
Fpresent to be of universal presence in sour paste. F. K. ex- 
Plains in “ Science Gossip,” that the paste must be made of pure. 
flour and water, boiled, and quite thick. It must be stirred every 
day with a wooden spoor, and the “eels” will appear in a few . 
days in warm weather, but after a longer time incold. The supply 
may- be kept for years by adding a little fresh paste occasionally. 
Tue Ortéry or “t Guano.” — The accepted theory of the nature 
or this familiar fertilizer was combated by Professor A. M. Ed- 
wards, at a meeting of the New York Lyceum of Natural His- 
He considers it a sediment, consisting of both vegetable 
and animal organisms, which formed at the bottom of the sea and 
Was subsequently elevated as well as chemically changed. The 
de $ preservation of the diatomaceous shells is adduced as evi- 
nce in favor of this theory. 
ÅRBORESCENT Sttver.— The beautiful specimens known by this 
ae may be easily produced by the following method which is 
t ned from “ Science Gossip.” A drop of a very weak solution 
o ‘trate of silver is placed on the centre of a slide, and a piece of 
