APRIL 22, 1807 | 
reproduce the pictures of the portrait lens as a chart 
of it. 
This is an example of what portrait lenses have given 
us’ in quite a new direction. If we find out, as in this 
case, that two such nebulze are connected in spite of their 
being far distant on the sky, this gives us the impulse for 
quite a new comprehension of the universe ; and all the 
theories of this kind have to be given up in favour of a 
new one. 
I gave other examples of such 
large nebulae several years ago 
in Anowledge, and perhaps they 
are still in the memory of some 
of the readers. 
An example of the connection 
of a cluster with the Milky Way, 
and the general structure of a 
part of the same, is given in 
Fig. 2. The cluster is Messier 
11,in Scutum, exposure 3} hours, 
enlarged part of the original 
plate. It will be seen at first 
sight, that those mighty masses 
of faint stars and star dust show 
the most interesting stratifications 
and connections. The cluster 
looks like the centre of a moved 
system. We see here ata glance, 
that it would have been impos- 
sible to get such views of star 
streams with the small field of a 
reflector. 
I use this opportunity to state 
that I made last year several 
improvements in finding and re- 
producing nebulous masses, using 
a method of strengthening the 
image by reprinting it. It is 
possible—by printing the original 
plate successively on other plates 
—to reinforce the feeble contrasts 
between the nebulosities and the 
background of sky, so that one 
can see at a glance such nebule 
on the reproduction, of which the 
traces are only to be suspected 
on the original plate. It looks 
very curious to see side by side 
the original and the reproduced 
negative. My friend Prof. Nae- 
gamvala, to whom I communi- 
cated the method last year, has 
published something about this 
matter in the Journal of the 
British Astronomical Association 
(vol. vil. No. 3). He and Mr 
Lunt had ereay success with the 
nebula M.8, using this method. 
The reprinting ought to be done 
upon slow plates in over-ex- 
posing, and, in developing, very 
slow developers should be used. 
NATURE 585 
reproduction of the nebula, so only one illustration is 
given. : 
For another example I give the outer-nebule of the 
great Orion nebula (4), which are reproduced here the 
first time (Fig. 4). Wesee many interesting streams of 
nebulosity all around, which never thus can be given at 
once by a reflector. The print is from an enlar; gement 
ee a negative of 44 hours’ exposure, with a 6-inch portrait 
ens. 
I give here (Fig. 3) the twice 
reprinted reproduction of a plate 
of the Andromeda nebula, as an Fic 
example of the results obtained. 
The original (of four hours’ ex- 
posure witha 5 5-inch aplanatic lens, made in 1891) was very 
faint. so that it would have been impossible to make a 
good print of it. It is not possible to go further on in 
this way, because the grain becomes troublesome. But 
using transferrotype- collodion- paper or dry-collodion- 
plates, the process can be repeated several times. 
The process used for reproduction is unable to make 
a satisfactory comparison between the first and second 
NO. 1434, VOL. 55] 
4.—The surrounding nebulz of the Great Orion nebula. 
In spite ot using this small 6-inch lens, nearly all detail 
visible in brighter parts photographed on Dr. Roberts’ 
photographs is quite well visible here. It must be pos- 
sible to get, within a certain limit, detailed pictures of 
nebulze by portrait lenses. No doubt, a good and large 
reflector will give much more detail ; but the difference 
between reflector and portrait lensis not so great as is 
often supposed. The sharpness of the image of the portrait 
