August 27, 1885 | 
of the uses of this deflector, which is an important point 
to those desirous of using the instrument. 
In four chapters of his Practical Guide M. Collet has 
given, in detail, practical rules for correcting the errors 
of the compass without bearings, illustrated by numerous 
examples, and including instructions for the graduation of 
the deflector, or measuring the magnetic force for each 
division of its scale. Collected in a tabular form, the 
results of this graduation will be found of great use to 
observers, and of the five advantages arising from it 
enumerated by the author, not least is that which gives 
an approximate value of the coefficients of deviation. 
This would prove useful when the observer, wishing to 
leave the magnets undisturbed, required only to know if 
any change of deviation had taken place. 
Another advantage of this graduation is that it forms an 
additional method of measuring the diminution of the mean 
directive force of the compass on board ship as compared 
with that on land, or the term J of the text-book. Ais a 
necessary element in the exact correction of the heeling 
error—a part of the correction to which the author de- 
votes a chapter, as it rightly comes under the denomina- 
tion of a compensation requiring no bearings. 
Lieut. Collet, in his introductory chapter and elsewhere, 
strongly urges that the deflector, concerning the uses of 
which he has written so fully, should in the immediate 
future become the chief instrument used in the compen- 
sation of compasses, on account of the rapidity and 
sufficiency of precision with]which it may be made, and 
that it be adopted for frequent if not daily use on board 
ships at sea. Before remarking on this proposal it may 
be as well to inquire into the present customs with regard 
to the standard or navigating compass at the time of its 
first compensation and subsequent changes of deviation. 
In the Royal Navy the adjustment of compasses is 
invariably made by bearings, and the instances are rare 
when the adjustments of the standard compass alone, 
including the final swinging of the ship, occupy more 
than an hour or two with results absolutely correct. Sub- 
sequently to this one adjustment the compensating mag- 
nets are not moved during their three or four years’ 
period of service, but the deviations of the compass are 
carefully observed on all occasions when bearings can be 
taken—in other words, from day to day—and noted for 
guidance when bearings cannot be taken. In the Mer- 
cantile Marine a large number of ships are fitted with Sir 
W. Thomson’s standard compass with the accompanying 
magnets adjustable at pleasure. This compass is often 
compensated by experts in the use of the deflector and 
the magnets left in a given position. 
Now, what is the almost universal practice of the com- 
manders of these vessels subsequent to this adjustment 
by means of the deflector? They observe the deviation 
frequently by day and night when possible, note the | 
results in a compass journal for present and future 
guidance, and object most strongly to any alteration of 
the magnets. 
In the paragraph headed “ Weather” it will be seen 
that a moderately smooth sea is required when using the 
deflector, and in another place it will be seen that it is no 
certain guide to navigation unless observations are made | 
on all the cardinal points. The question therefore arises, 
Are the necessary conditions for using this instrument 
NAPUOR 
387 
often available in the North Atlantic and “roaring 
forties,” when bearings are at times unobtainable for some 
days? 
The result of the foregoing consideration is to show 
that there is long custom of very practical men—and pos- 
sibly prejudice—to overcome before Lieut. Collet’s future 
of frequent use of compensation without bearings becomes 
general. 
The nautical world has had the deflector as invented 
by Sir W. Thomson before it for some years ; it now has 
an excellent practical guide to its use in the book under 
review, and it remains to be seen how far that world will 
avail itself of the invention. 
It may probably suggestitself to some mindsthat the book 
would lose none of its value by being shortened somewhat 
in detail ; indeed, the shorter the better, if combined with 
accuracy for the practical navigator, and should a new 
edition be required the translator who has done his part 
well, and knows the deflector thoroughly, will perhaps try 
his hand at the work of condensation. 
THE FORBES MEMORIAL VOLUME 
In Memoriam. The collected Scientific Papers of the 
late William Alexander Forbes, M.A., Fellow of St. 
John’s College, Cambridge, Lecturer on Comparative 
Anatomy at Charing Cross Hospital, Prosector to the 
Zoological Society of London. Edited by F. E. Beddard, 
M.A., Prosector to the Zoological Society of London. 
With a preface by P. L. Sclater, M.A., Ph.D., F.R-S., 
Secretary to the Zoological Society of London. (London: 
R. H. Porter, 1885.) 
HE death of Alfred Henry Garrod at the early age of 
thirty-three was a great misfortune to the cause of 
zoology in this country. But that his distinguished suc- 
cessor, William Alexander Forbes, a man full of vigour 
and in the best of health, should have suddenly suc- 
cumbed to the influence of a pernicious climate at 
the age of twenty-eight, was perhaps a still more severe 
blow, and one that will long be felt by the naturalists of 
the present day. We do not seek to compare Forbes 
with Garrod, but it must be recollected that Forbes was 
a man of undoubtedly strong physique, for whom there 
was every prospect of a long and successful career. There 
can be not the slightest doubt that, had he not lost his 
life from the accidental force of circumstances, Forbes 
would have left a considerable mark on the progress 
of science. As regards natural history at least, if 
not in some other matters, Forbes was a universal 
genius. Of the whole zoological series he had an 
enormous knowledge, ranging from one end of the animal 
kingdom to the other. Possessed of a most retentive 
memory and of an abundant stock of energy, he 
was unremittingly at work on his favourite subject, 
and never forgot what he had acquired either by reading 
or by experience. Not only was he thoroughly up in 
zoological literature, but he was also an accurate observer 
and a diligent collector in the field, where nothing came 
amiss to him. Mammals, birds, butterflies, and beetles 
were perhaps the groups which he knew best ; but Forbes 
had, as already stated, an excellent general knowledge of 
the whole animal series. Whatever novel object might be 
shown to him he was very rarely at a loss for its 
