100 NOTES AND MEMORANDA. 
sent a beauty in their resolution that excites the highest admiration. 
In comparing its capabilities with a number of the objectives of the 
most distinguished makers, it certainly had the advantage. Its focal 
length is quite short, and consequently requires very thin covering 
glass.” 
The Fossil Earth of Richmond, U.S.A.—This appears to be an 
exceedingly rich deposit, and it may be worthy of examination by 
some of our readers who may have the opportunity of possessing 
specimens. The ‘ American Naturalist, of December last, says of it 
that the recent excavation of a tunnel by the Chesapeake and 
Ohio Railroad Company, through that part of the city of Richmond, 
Va., known as Church Hill, has intersected this famous deposit for a 
distance of three-fourths of a mile, and afforded rare facilities for 
study and the collection of material. C. L. Peticolas, of Richmond, 
who has given great attention to the work of obtaining this interesting 
material and preparing it for use, describes the stratum as from forty 
to sixty feet thick, and situated, nearly level, about fifteen to twenty- 
five féet below the level of the city, and one hundred feet above tide 
water. Before exposure to the air it is tough and hard, having the 
colour and solidity of bituminous coal and requiring to be removed 
from the tunnel by means of blasting; but after exposure for some 
time it crumbles to a fine powder of almost snowy whiteness, con- 
sisting in general of about one-half fine pure clay, one-fourth fine 
white sand, and one-fourth fossil diatoms interspersed with many 
sponge spicules and a few Polycystina. The abundance and variety 
of the fossil forms vary greatly in different parts of the stratum, the 
lower levels being the richer. 
The Blood-stain Controversy.—We have received a copy of the 
‘ American Medical Times’ from Dr. Richardson, with a request that 
we would notice a discussion, that it reports, in the Academy of 
Natural Sciences of Philadelphia, on the subject of the microscopic 
detection of human blood-corpuscles. But it seems to us that Dr. 
Richardson is unquestionably wrong in this matter. We have gone 
carefully into the subject, with the aid of the magnificent photographs 
taken from micrometer slides with blood drops on them, which Dr. 
Woodward sent us, and we have not the slightest hesitation in saying 
that the blood of man is absolutely indistinguishable, by our present 
means, from the blood of the dog or guinea-pig. 
The ‘Science-Gossip’ Section Machine bids fair to have a great 
reputation. The ‘American Journal of Microscopy’ (January 1877) 
reprints the paper with the cut which recently appeared on the 
subject in ‘ Science-Gossip ’ itself. 
Typical Specimens of the Diatomaceze.—The ‘ American Journal 
of Microscopy’ (January 1877) has an important article on this sub- 
ject, from which we may quote as follows :—“ We have just received 
from Professor Hamilton L. Smith, of Hobart College, Geneva, N.Y., 
the first century of his ‘ Diatomacearum Species Typicex,’ and have 
rarely had a greater treat than was afforded by the examination of this 
collection. Most microscopists are familiar with the celebrated 
‘Typen Platte’ of Méller, an exquisite production of artistic skill. 
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