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POPULAR SCIENCE REVIEW. 
an exact copy of Colonel Perronet Thompson’s Monochord , hearing a weight 
of 240 lbs. to produce Tenor C, and Professor McLeod’s ingenious modifica- 
tion of Lissajous’s figures in the cycloscope. He laid much stress on the 
computative method, on account of its extreme simplicity and accuracy. 
By it absolute was first obtained from relative pitch. Scheibler’s Tonmesser 
and Appunn’s reed-tonometer were exhibited, as well as a photograph of 
Koenig’s tuning-fork clock. 
3. The problem of absolute pitch having now been satisfactorily deter- 
mined, its application only needed time and patience, the present state of 
the matter being discreditable to England. Since Handel’s time, pitch had 
risen about a semitone. This was attributed to (1) the excess of true fifths, 
as tuned to by violins, over the corresponding octaves ; (2) the rise with 
heat of the wind instruments ; (3) the difficulty of appreciating slow beats ; 
(4) the predominant effect on the ear of a sharp over a flatter note. The 
voice — God’s instrument — should be consulted in preference to man’s less 
perfect instruments. The difference, however, between the present high 
orchestral pitch and the French normal diapason which, as a standard, had 
been proved to be both accurate and convenient, is less great melodically 
than is often supposed. Indeed the ear, unassisted by beats, was all but 
unable to detect the difference. The main need of modern music was a 
greater familiarity with the physical principles upon which it rests. 
ZOOLOGY. 
Abyssal Crustacea of the West Indies. — Prof. A. Milne-Edwards has laid 
before the French Academy of Sciences a general statement of the results of 
his investigation of the Decapod Crustacea dredged up from great depths in 
the West Indian seas, by the U. S. exploring- ship Blake (Comptes Bendus, 
21 February, 1831). 
The family Galatheidae has always been regarded as wanting in American 
waters ; among these collections there are forty-one species, mostly consti- 
tuting new genera, although thirteen of them belong to the widely distributed 
genera Galathea (2) and Munida (11). True Crabs do not occur at very 
great depths ; numerous small species are found down to about 250 fathoms, 
and at about 400 fathoms a new form allied to the well-known European 
genus, Gonoplax, was obtained. This animal, deecribed by Prof. Milne- 
Edwards under the name of Bathyplax, is blind, its eyes being atrophied and 
destitute of facets, and its orbits rudimentary. The Anomurous and Ma- 
crurous Decapods, on the contrary, swarm at great depths. Down to about 
1800 fathoms the curious genus Willemoesia was represented ; its species are 
apparently most nearly related to the well-known Eryons of the Jurassic 
rocks, but the deep-sea forms examined by M. Milne-Edwards were blind. 
The Galatheidae already mentioned occurred at still greater depths, down 
to more than 2000 fathoms, from which depth came species of a 
new genus ( Galathodes ) having the eyes greatly reduced and imperfectly 
facetted. The most interesting types are those belonging to the family 
Paguridae, represented hitherto by the well-known Hermit Crabs, which, 
