SCIENTIFIC SUMMARY. 
323 
binocular vision. The objective — I take an ordinary object-piece, and by a 
circular saw divide it along its line of collimation, and afterwards rejoin the 
halves by screws and steady pins, until as an objective it is in as perfect a 
state of adjustment as before division. It is then capable of acting as an 
objective for one or two eyes, according to the position assumed by the two 
halves under the control of the mechanical part of the instrument when the 
direct light is stopped out. According to another method, I work the lenses 
of an achromatic object-piece out of divided and rejoined discs of glass, 
which when finished and fixed in a divided mounting temporarily held to- 
gether for that purpose may be afterwards separated by dissolving out the 
cement by which the halves of the discs were originally conjoined. Or 
lastly, I make two whole object glasses, and fix one into each half of a 
divided mount, cutting away only such portion as will allow of proper 
approximation. This method is available for high powers and for binocular 
use only. In all cases I cut the usual screw-thread on the objectives to affix 
them to the body, and more surely sec ire their halves in their respective 
places in the divided body tube of the instrument by two small milled- 
headed screws.” 
Mr. Stephenson's new Erecting Binocular . — Of all the inventions which 
have been made since Mr. Wenham brought out his original prism for 
the binocular, that which has been described to the Royal Microscopical 
Society at its last meeting (June 8), by Mr. Stephenson, is the most remark- 
able. This new binocular has been used with powers as high as --inch 
(immersion), with excellent results, and it promises to be an instrument 
superior even to the u Wenham.” We must not anticipate the description of 
the instrument which is to appear in an early number of the Monthly Micro- 
scopical Journal [the microscope is now, we believe, being made by Messrs. 
Ross, the eminent opticians, of Wigmore Street] ; but we may give a report 
of some of the remarks made by those who examined the instrument at the 
last meeting of the society : — Mr. Brooke said that from his observation of a 
fly’s tongue exhibited under Mr. Stephenson’s microscope, it appeared that 
the definition was not at all interfered with by the peculiar construction of 
the instrument. The two fields presented to the two eyes were equally 
illuminated by the two pencils of light diverging equally from the object, 
instead of being thrown off obliquely, as in Mr. Wenham’s arrangement. 
The binocular effect produced also is more perfect than in the ordinary in- 
strument. The two horny processes by which the fly’s tongue is articulated 
and the series of tubes of which it consists were very well defined. — Mr. 
Slack said he had been struck with the perfection of the definition given by 
Mr. Stephenson’s microscope, and the equality of the illumination in each 
tube when low powers were employed. With a power of |rd only part of 
the field was illuminated, but that portion afforded most admirable defini- 
tion, and no noticeable errors were occasioned by the light impinging upon 
the edges of the prisms. It was certainly a very valuable invention. — Mr. 
Lee said he wished to correct the impression that Mr. Stephenson’s micro- 
scope could be satisfactorily employed only with low powers. He had 
made examinations with Gundlach’s — immersion lens (about equal to a —jth 
of the best English makers) which were quite satisfactory, the definition 
not being interfered with in any way. He believed that Mr. Stephenson had 
