128 
POPULAR SCIENCE REVIEW. 
New Printing Process. — Mr. Palmer, of Stonehouse, Devon, by employing 
gelatine instead of collodion, as suggested by Mr. G. Dawson, of King’s 
College, lias perfected a very beautiful process of printing on paper or opal 
glass, which will take rank with the very best of the new printing processes 
recently introduced. Mr. Palmer’s process is based on the suspension of 
chloride of silver in gelatine. 
PHYSICS. 
Physical Phenomena of the Hydrogen Flame. — Mr. W. F. Barrett, of the 
Royal Institution, has published some curious observations of the effect of 
contact of a hydrogen flame with various bodies. When conducting some 
experiments last spring, in which the hydrogen flame was directed against 
certain bodies, a peculiar blue colour was produced. A careful examination 
of this blue coloration showed that it occurred only when the flame came into 
actual contact with the substance, the colour being restricted with great pre- 
cision to the place where the hydrogen was in combustion ; accordingly, it 
gave in section a faithful image of the construction of the flame. This singular 
appearance was invariably of a rich blue tint ; its production was instan- 
taneous, but its duration was generally short, for it disappeared after a few 
seconds’ exposure when the flame continued to play upon one spot, although 
it was immediately restored by shifting the position of the jet to an untried 
portion. A classification of the substances employed yielded no satisfactory 
clue to the cause, even blocks of ice exhibiting the peculiar colour. Several 
experiments were made in vain to discover the source of the phenomenon, 
till at length an accident revealed it. “ Amongst the various substances I 
examined,” says Mr. Barrett, “ I found round that vulcanized india-rubber, 
when exposed to the flame, exhibited the blue colour with great brilliancy. 
But here I had reason to believe the blue colour was occasioned by the com- 
bustion of the sulphur with which the india-rubber is associated. To see if 
such were the case, a plate of platinum had its surface rubbed with a stick of 
sulphur, and was then exposed to the flame. Although no blueness was 
visible before, yet after the rubbing the coloration shone out brightly for a 
short time, having in every respect the same appearance as the luminosity 
seen on granite, &c. Afterwards I found that the slightest contact of sulphur, 
or a body containing it in the free state, was sufficient to impart to any substance 
the power of showing the blue coloration beneath the hydrogen-flame. When 
a plate of platinum which showed the blue colour from being wiped over with 
a piece of vulcanized rubber, was examined with a high power under the 
microscope, some spots were seen which were unaffected by a drop of water, 
but which readily dissolved in bisulphide of carbon. These and other ex- 
periments convinced me that, at any rate, the chief part of the phenomenon 
must be attributed to . the presence and combustion of minute quantities of 
sulphur.” The writer concludes bysupposing that sulphur being present in the 
