SCIENTIFIC SUMMARY. 
447 
ready for tlie artist. By means of this simple '"contrivance drawings"* of 
specimens in liquid (Infusoria, &c.) may be readily taken, and we believe 
the cost of the apparatus is not great. This accessory was devised by Dr. 
Purefoy Colies, of Calcutta, late editor of the Indian Medical GazettCy and 
was prepared at Dr. Lawson’s suggestion by Mr. Collins. 
A Reversible Compressorium of an ingenious kind has been invented by 
Mr. S. Piper. It is something like Beck’s reversible compressor attached to 
a horizontal rod which slides and rotates through a universal joint. It 
appears from the published drawings to be a most useful and convenient 
apparatus. It is made by Mr. Swift, 15, Kingsland Boad, N. 
A Condtmser with a hlue-tmted Field Lens is also made by the above manu- 
facturer, on a plan suggested by Mr. W. H. Hall. Its advantages are thus 
summed up by its inventor in a paper before the Boyal Microscopical Society. 
(1) It can be used with advantage with from 2-inch to ^-inch objectives. 
(2) It gives fine daylight softness. (3) It is an effective spot-lens and 
dark-ground illuminator, with polarized light. (4) The change from one 
form of illumination to another is made with great ease. 
Noherfs Test Plate. — Those who are desirous of knowing what fractional 
part of an inch is made visible by the highest powers of our modern micro- 
scopes should read an interesting paper reprinted in the Quarterly Journal of 
Microscopical Science y July, from the American Naturalist. It is written by 
Mr. Charles Stodder.j 
PHOTOGRAPHY. 
The British Association at Norwich. — Photography played a very minor 
part in the proceedings of the British Association for the Advancement of 
Science this year. The Report of the Kew Observatory Committee showed 
numerous and important applications of the art, and of their satisfactory 
nature. In section A. Mr. Bing described a new actinometer. It consisted 
of a rectangular tube of non-actinic glass, with an arrangement for bring- 
ing into contact with one side of the interior a strip of paper previously 
rendered sensitive to the action of light. The tube being placed in diffused 
light, with its open aperture exposed to the sky, the light darkens the paper 
in the ratio of its quantity, which necessarily diminishes as it proceeds 
farther into the tube, inside which, by the sensitive paper, is fixed a scale 
with divisions, marked by a portion of a faint standard tint. In the same 
section Professor Morren introduced a paper entitled Sur une Action par- 
ticulihre de la Lumiere sur les Sels dU Argent. It contained nothing new. 
New Carbon Printing Process. — Mr. William Blair, of Perth, has an- 
nounced a new carbon process, the results of which — although it is"not yet 
perfected — give great promise. The great advantage is, that the troublesome 
process of transferring used in other carbon processes is done away with. 
The process, briefly hinted, consists in substituting a white tissue for the 
ordinary black one, and mounting it upon a black instead of a white sur- 
face. 
Neio Kind of Photographs. — A species of toy photograph has recently 
received some notice. It is obtained by coating paper or glass with a layer 
