April 19, 1883] 
NATURE 
577 
electrical discharges or thunderstorms, and this conclu- 
sion is amply confirmed by similar observations made in 
other parts of the globe. A very large number of these 
cases of sheet lightning at Oxford are, as suggested by 
Prof. Loomis in 1868, due to the escape of the electricity 
of the clouds in flashes so feeble that they produce no 
audible sound, and they occur when the air being very 
moist offers just sufficient resistance to the passage of 
the electricity to develop a feeble light. 
SALVADORI?S PAPUAN ORNITHOLOGY 
Ornitologia della Papuasia e delle Molucche, di Tommaso 
Salvadori. Parte terza. 4to. pp. 597. (Torino, 1882.) 
HE completion of the third and concluding portion 
of Count Salvadori’s great work upon the Birds of 
New Guinea and the adjoining Islands is an event that 
should be duly chronicled. We have already spoken of 
_ the plan of this great undertaking, and of the excellent 
| way in which it has been carried out, in our notices of the 
preceding volumes (see NATURE, vol. xxiii. p. 240, and 
vol. xxiv. p. 603). We will now say a few words upon 
the general results arrived at. 
The ground covered by the present work embraces, it 
| must be recollected, the whole of the northern portion of 
| the great Australian region. 
The mainland of this dis- 
trict is New Guinea, but it also contains the islands of 
the Moluccan Archipelago up to “ Wallace's Line,” 
besides various groups situated to the east and south-east 
of New Guinea, and extending as far as the Solomon 
Islands. In the ‘‘ Papuan Sub-region,”’ as it is generally 
called, thus constituted, it will be evident that variation 
must necessarily play a much more important part than 
in the solid continent of Australia. Not only do the 
species isolated in the different islands obtain a better 
' chance for the exaggeration of their peculiarities (as has 
been so well shown by Mr. Wal'ace in his “Island Life”), 
but in the mainland of New Guinea we find mountains 
reaching to such an altitude as to cause the presence of a 
very different fauna from that of the adjoining lowlands. 
From these two causes it would be naturally expected 
that the ornithology of the Papuan Sub-region would be 
more rich in species than that of Australia proper. And 
such, indeed, is shown to be the case by the completion 
of Count Salvadori’s work, whereby the first summary 
has been effected of the Papuan Crnis, since recent 
researches have revealed to us its luxuriance. In Mr, 
Gould’s great work upon the Birds of Australia little more 
than 700 species of birds are given as inhabitants of the 
whole of that great continent. By Count Salvadori’s 
volumes, we find that 1028 species are already known to 
us from the Papuan Sub-region, and, as we all know, a 
very large portion of New Guinea and many of the 
adjacent islands are still fexva zncognita. Much therefore 
remains to be added to the Papuan Avi-fauna, whilst in 
Australia the subject is comparatively exhausted. 
Taking a general survey of the forms of Papuan bird 
life, we see at once how nearly akin it is to that of 
Australia. Recent researches especially have shown that 
nearly all the peculiar forms of the Australian Ornis have 
their representatives in the Papuan Sub-region. Some 
of these forms, however (for example, the Paradise-Birds 
and the Cassowaries), are much better represented in the 
Papuan Islands than on the Australian Continent, and the 
Papuan Islands must be regarded as their original home, 
whence they have sent forth stragglers into the Southern 
Continent. 
Such general facts as regards the distribution of bird 
life in the Australian Region may be easily gathered from 
an inspection of the contents of the present work. But 
our author, we are glad to see, promises us to put them 
forward in his own shape, in an “Introduction to the 
Ornithology of Papuasia and the Moluccas,” which he is 
now preparing. In this supplementary volume will be 
likewise given chapters on the history and bibliography 
of the subject, and a chart to illustrate its somewhat 
complicated geography. Count Salvadori is evidently 
determined to spare no trouble in order to render com- 
plete the results of his eight years’ hard labour on the 
Birds of Papuasia and the Moluccas. 
OUR BOOK SHELF 
Cutting Tools Worked by Hand and Machine. By 
Robert H. Smith, M.I.M.E. (London: Cassell, 
Petter, Galpin, and Co., 1882.) 
STUDENTS of mechanical engineering, and more espe- 
cially those who study machine tool construction, have 
up to the present time found it very hard to obtain a suit- 
able text-book relating to the theoretical part of the 
subject ; hitherto almost the only books relating to it 
have been published in Germany. 
This work comes to hand at a time when the want 
of such a work is much felt, and students attending 
mechanical engineering classes will find that it will help 
them considerably in understanding the construction, 
theoretically and practically, of the machines dealt with. 
The author in his preface states distinctly that he does not 
intend the book to be a descriptive treatise on tools, nor 
does he refer to all the different cutting tools in use, but he 
has happily chosen the more important machines, and 
gives a very full description and illustration of each. The 
subject of driving power is dealt with and fully explained, 
and results of experiments carried out by the author on 
the subject are carefully arranged in tables. 
In the first chapters cutting tools for wood are dis- 
cussed, the wedge action of any cutting tool being 
clearly described and illustrated ; also the method of 
grinding and setting edge tools, frequently a very difficult 
task for beginners to accomplish. He also gives the 
results of experiments carried out by himself on the 
power required to be exerted through certain tools when 
doing a fixed amount of work, an interesting subject from 
a theoretical point of view. 
The chapter on chipping-chisels and hand-planes fully 
explains the action and construction of the several tools, 
the different angles of the cutting-edge of cold chisels are 
shown, and the author points out the reasons for varying 
the angle according to the quality of the metal. The whole 
chapter goes into the subject practically, the explana- 
tions being clear and to the point. The next chapters 
deal more especially with wood-working machinery. The 
variety of teeth used in the different kinds of saws, 
including inserted teeth, are amply illustrated, the 
important matter of setting the teeth being fully ex- 
plained, with experiments showing the power absorbed 
in driving the different saws, this also being usefully 
arranged in tables; after which the author goes on to 
explain the different machines used in working the 
metals, milling machinery having its full share of the 
text. The cutting speed and rate of feed for milling- 
cutters is gone into, and in the latter part of the chapter 
the milling-cutters themselves are dealt with. i 
Chapter V. relates to the various methods of planing 
