NATURE 
[ Oct. 28, 1886 
THE GERMAN NAVAL OBSERVATORY} 
T will be remembered by our readers that in the spring 
of the present year a review of the sixth yearly Re- 
port of the German Naval Observatory at Hamburg was 
given (NATURE, vol. xxxiii. p. 411), in which the objects 
and the general system of working in the several depart- 
ments, as well as some special papers on subjects con- 
nected with the Cbservatory, were noticed. 
In this, the seventh yearly Report, there is the same 
evidence of the progress of useful work in all departments 
described in the first of the four papers which it contains, 
but not requiring special remark. In Paper No. 2, how- 
ever, there is a detailed account of the building in which 
this work is carried on, and a general description of the 
instruments employed, which can hardly fail to be of 
interest even to those who may have personally visited 
the Observatory. 
The traveller approaching the docks of Hamburg by 
the Elbe, will see a square sandstone building in the 
Renaissance style situated on an eminence which rises 
abruptly 100 feet above the river, between Altona and 
Hamburg. This is the Naval Observatory, in an excel- | 
lent position for observations, and commanding an exten- 
sive view of surrounding objects for many miles, close to 
the shipping for the welfare of which it was chiefly esta- 
blished, and as it were inviting the commanders to come 
and partake of the advantages held out to them. The main 
building—which in plan forms a hollow square, and con- 
sists of a basement, ground floor, and two stories above, 
with ample internal galleries and staircases for commu- 
and completed in October 1881, 
the lower rooms having 
month by the Emperor of Germany in person. 
Over the principal entrance, which faces towards the 
south-west, are three busts of well-known scientific 
worthies, that of Dove being in the middle, with Maury 
and Riimker right and left. The square inside the build- 
ing is roofed with glass, giving protection to the galleries 
and the Combe apparatus which occupies the floor, whilst 
it proves but a small obstruction to the light. 
A view from the north-west side of the building will be 
found on Plate 1, and on Plate 2 a plan showing the 
general disposition of the adjoining structures. 
Preceded by some historical references to the site now 
occupied by the Observatory—where fortifications for- 
merly existed—in pp. 5-12 will be found a description of 
the uses to which the various rooms are devoted, with 
references to the twenty-nine excellent plates, showing 
their size, and the mounting of the various instruments 
in them, both in elevation and plan. At each angle of 
the building there is a low square tower. On the western 
of these the anemometers and wind-vane are mounted, 
with electrical communications to the registering appar- 
atus. Inthe south tower is the apparatus for proving 
sextants, for which the known angles between well-defined 
distant objects are used, it being a rare occurrence for the 
latter to be obscured by fogs. A transit instrument occu- 
pies the eastern tower, and an alt-azimuth instrument the 
northern. 
From pp. 12-26 detailed accounts are given of the 
principal normal and self-registering instruments, the 
laboratory, the compass observatory, and the museum 
with its contents. Amongst the special apparatus a regis- 
tering rain-gauge is described at p. 27, with an illustra- 
tion ; this, with the sliding-weight barograph described on 
p. 29, was designed by Dr. A. Sprung. 
The magnetic pavilion in the garden is chiefly devoted 
to experimental determinations of the induction-co- 
efficients for various kinds of iron, and instruction to 
students in magnetism. 
a Naval Exhibition in 
been opened in the previous 
* © Aus dem Archiy der Deutschen Seewarte.” 
f e n VII. Jahrgang, 1884. 
Herausgegeben von der Direcktion der Seewarte. 
(Hamburg, 1886.) 
| of the observations made by Dr. 
"a voyage from Germany to Australia by 
Some remarks on the uses of the Combe apparatus, 
founded on information of a later date than that of the 
present Report, may possibly be of interest. A doubt has 
already been expressed (NATURE, vol. xxxiii. p- 411) as 
to the value of the effects produced on chronometers by 
| machinery for simulating the rolling and pitching motion 
of a ship at sea. This doubt has been confirmed by 
experience, and some additions have been made to the 
apparatus by which the effects of shaking such as might 
be caused by the racing of the engines on board ship or 
the blow of a heavy sea are introduced. These effects 
of shaking are clearly shown in the rates of the chrono- 
meters tried. 
As the Combe apparatus can be rapidly revolved by 
means of a gas engine, its uses have been extended to the 
trial of anemometers and the measurement of wind- 
pressure, the arrangements for which may be seen on 
Plate 18, and a description of the same on pD. 12-15. 
It is reported that the results obtained are satisfactory 
with the exception of minor effects on the anemometers 
caused by draughts passing through the arched openings 
to the adjoining corridor, but this is in a fair way to be 
accurately accounted for. 
In Paper No. 3, the course of instruction used by 
students at the Observatory on the mathematical treat- 
| ment of the deviation of the compass, with examples, is 
| shown in detail. 
A certain knowledge of mathematics 
and mechanics is required of the students preliminary to 
this instruction, but they have the assistance of Dr. Neu- 
mayer’s deviation model (NATURE, vol. xxxiii, p- 587) for 
cereale : : 0 | experimental illustration. 
nication with the various rooms—was commenced in 1879 | 
The formulae used are, with one exception, those of the 
Admiralty Manual for Deviations of the Compass, pub- 
lished in London in 1869. 
The exception will be found on pp. 29 and 30, where it 
may be seen that a new term is introduced into each of 
the equations representing the fore-and-aft and transverse 
magnetic forces of an iron ship. The object is to givea 
mathematical expression for the temporary changes which 
are produced in an iron ship’s magnetism when her course 
lies in a given direction for a few days, or even hours, 
under certain conditions—the change only becoming 
apparent on alteration of the course. The amount of 
change experienced depends upon the quality of the ship’s 
iron, the position of the compass, the length of time she 
is kept on the given course, the degree of shaking she is 
subjected to during that time, and is proportional to the 
earth’s magnetic force at her mean geographical position, 
The question is more fully discussed in the Aychiz der 
Deutschen Seewarte for 1879, No. 4, where some values of 
the changes denoted by the constants / and l’’ for certain 
ships are tabulated, but these values are dependent on so 
many contingencies, that nothing but carefully-conducted 
observations systematically made for each ship can give 
exact results. It may be remarked, however, that from 
results of the kind just described properly analysed, much 
useful information might be deduced and furnished to 
iron vessels proceeding on a voyage, as to the probable 
changes in their magnetism under various conditions. 
The general rule at present is to depend entirely on 
observations of the deviations of the compass and their 
registration for future guidance when observations can- 
not be obtained. There is much to be said in favour of 
this rule, but there is also much to be hoped for from the 
more scientific treatment. It may be added that as 
similar results are often obtained in vessels of like types 
of construction, the analysis of observations from many 
vessels is much to be desired for the guidance of com- 
manders of vessels starting on their first voyage, possibly, 
in weather when objects on land or in the sky are 
invisible. 
In the fourth and concluding paper an account is given 
Richard Neuhauss during 
the Suez Canal 
tir We ew 
