594 
NATURE 
[ Oct. 21, 1886 
of irregular appearance, 80 as stragglers, and 6 as doubt- 
ful. Two “ ornithological calendars,” one giving the times 
of “migration” and the other those of “ nidification,” 
add considerably to the value of this useful work, which 
must not only of necessity be in the hands of every Italian 
ornithologist, but which every student of the European 
Ornis, or of any constituent parts, should have for refer- 
ence. We trust that the good example thus set by Eng- 
land, America, and Italy will lead to the publication of 
other similar hand-books. 
OUR BOOK SHELF 
The Law of Storms, considered practically. By W. H. 
Rosser. Second Edition. (London: Norie and Wilson, 
1886.) 
WE welcome with much pleasure the second edition of 
this useful little work on storms practically considered. 
The first edition, briefly noticed by us at the time (vol. 
xiv. p. 504) appeared ten years ago. Since then the 
researches of meteorologists have materially advanced 
the science, notably in establishing on a firmer basis the 
law of the in-moving spiral circulation of the wind in 
cyclones, and defining with some exactness the limits of 
variation of the angle of inclination of the winds as they 
blow inwards toward the centre of storms. In this view 
especially the last part of the work has been recast, 
recent investigations being summarised with no little 
ability, and the results thereafter applied to navigation. 
The book, which is professedly a practical one, is | 
specially and admirably adapted to give seamen the best 
available information in handling their ships in storms. 
Ueber Manatherium delheidi, eine Strene aus dem Oligo- 
cain Belgiens. Von Dr. Clemens Hartlaub, Zool. 
Jahro., vol. i. (1886). 
Dr. CLEMENS HARTLAUB’S excellent contributions to our 
knowledge of the recent Sirenians have lately been 
noticed in these columns (July 8, p. 214). We have now 
before us his essay on an extinct form of the same 
peculiar group of mammals. The luxuriance of fossil 
forms of the Oligocene of Belgium is well known to all 
zoologists. Upon materials gathered from the Superior 
Rupelian beds of Hoboken, near Antwerp, which have 
already produced remains of Cvassztherium and Hali- 
therium, Dr. Hartlaub founds a new genus of Sirenians, 
nearly allied to the living Manatee, which he pro- 
poses to call anatherium. Its dentition, so far as it is 
at present known to us, does not materially differ from 
that of JZanatus, of which, indeed, it may have been the 
immediate progenitor ; and the necessity for its generic 
separation from its modern representative is perhaps not 
altogether evident. The species is named M/anatherium 
delheidi, from M. E. Delheid, in whose cabinet of Belgian 
fossils the remains upon which it is based are contained. 
Fossil species of true JZamatus have been described by 
Leidy and other authors in America, and M. Filhol has 
assigned some African remains to the same genus. But 
Manatherium delhetdi is at present the only European form 
described as belonging to this exact type of the Sirenians. 
LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions ex- 
pressed by his correspondents. Neither can he undertake to 
return, or to correspond with the writers of, rejected manu- 
scripts. No notice is taken of anonymous communications. 
[Zhe Editor urgently requests correspondents to keep their letters 
as short as possible. The pressure on his space is so great 
that it is impossible otherwise to insure the appearance even 
of communications containing interesting and novel facts. | 
The Tangent Scale in a Galvanometer 
On account of the correspondence which has recently taken 
place in this and other journals regarding the use of the tangent 
scale in a galvanometer, when the plane of the coil makes an 
angle with the direction of the force in the magnetic field, the 
following extract from Sir William Thomson’s patent, No. 4617 
of 1883, and the accompanying remarks, may clear up some of 
the points that have been raised :-— 
“*In using this instrument I sometimes cause the zero to be 
at one end of the scale, so that, when the potential is at the pre- 
scribed definite amount, the pointer is at the centre mark of the 
scale of tangents. The deflections are thus more easily ob- 
served, on account of the large size of the divisions.” 
This extract is quite explicit as to taking the zero at one end 
of the scale, and it is abundantly evident, from the text of the 
patent and from the illustrative drawings, that the scale referred 
to is a tangent scale. The essential feature in this use of the 
tangent scale is that the strength of the current is proportional 
to the difference between the tangents of the angle correspond- 
ing to zero and that corresponding to the deflection due to the 
current. 
The total length of the scale, as shown in the patent already 
referred to, and used in this Laboratory for over two years, is 
120°. Lately, however, the length of the scale has, with con- 
siderable advantage, been increased to 147°°8, thus giving twice 
the sensibility obtainable with the 120° scale. 
As regards Prof. Carey Foster’s letter to NATURE of October 
7 (p. 546), a tangent galvanometer arranged to use the tangent 
scale in this manner is essentially adapted to measure currents 
which flow through its own coil in one direction only, but in 
these instruments, as designed by Sir William Thomson, the 
necessary accuracy is secured by the following procedure. The 
index (which has a range of about 95° on each side the middle 
point of the tangent scale) is caused to point to a mark exactly 
go” from the middle point of the scale, and the relative positions 
of the coil and the scale are then adjusted, so that, when the 
index points to the go° mark, the strongest current which can be 
safely sent through the coil produces no sensible deflection. 
J. RENNIE 
Physical Laboratory, the University, Glasgow, October 16 
On the Connection between Chemical Constitution and 
Physiologi¢al Action 
In the address delivered by Dr. Brunton on this subject before 
the Section of Therapeutics and Pharmacology at the last 
meeting of the British Medical Association, a copy of which 
was published in NAtTuRE, August 19, p. 375, he observes, in 
alluding to the adoption of more scientific methods in pharma- 
cology :—‘' This may be said to have begun about twenty years 
ago, when the researches which my predecessor in this office, 
Dr. Fraser, made with Prof. Crum Brown upon the connection 
between physiological action and chemical constitution inaugur- 
ated a new era in pharmacology. ... We might first date the 
beginning of this age from Blake’s attempts to show that a 
connection exists between the forms in which the various bodies 
crystallise, and the mode in which they act on an animal body. .. . 
Nevertheless, I think we may fairly say that it was the experi- 
ments of Crum Brown and Fraser which fairly started pharma- 
cology in the new direction in which it has since been steadily 
advancing.” Now it can, I think, be shown that in these 
remarks Dr. Brunton has not only misunderstood the scope of 
my experiments, but that he has been led into error on account 
of his having no definite idea of the meaning of the term 
chemical constitution, which he has evidently confounded with 
that of chemical composition. The same confusion of these 
terms is not only apparent all through the address, but is also 
found in the paper on the subject by himself and Dr. Cash, 
published in the Zyansactions of the Royal Society, 1884. 
The term chemical composition is well understood, but the 
meaning of the term chemical constitution is not so well de- 
fined. Perhaps the difference between the two terms may be 
pointed out in the shortest space by an example. If we take 
the salts of iron, for instance, we know that the salts of the 
protoxide have a chemical constitution analogous to the other 
members of the magnesian group with which they are iso- 
morphous, and that this r:semblance in constitution connotes 
not merely that they crystallise in analogous forms, as Dr. 
Brunton seems to imagine, but also that they form many analo- 
gous chemical compounds which resemble those of the other 
members of the same group more closely than the compounds 
of any other group. By the addition of oxygen to the protoxide, 
not only is its chemical composition changed from FeO to 
POCew oe. 
