SCIENTIFIC SUMMARY. 
391 
explosions which occur in our coal-mines result from the utter recklessness of 
the workmen, who open their safety-lamps for various purposes. Mr. Foster’s 
lamp is constructed in such a manner that the ring or frame of the wire 
gauze when it is put into its place is caused to engage with a disk, which, 
when turned, raises or lowers the wick ; and on the gauze-frame is placed a 
spring catch, which, when the locking-ring is screwed into its place, hears 
against the interior. On this locking-ring is a catch which will only allow 
the spring catch to pass it in one direction, so that the gauze can only he 
turned (in order to raise the wick) so far as to bring the catch up to the stop 
on the locking-ring. In opening the lamp the locking-ring requires several 
turns to free its screw, and in the course of the motion the spring catch is 
brought up to the stop, the gauze is forced to turn, and the motion thus com- 
municated to it lowers the wick, and so extinguishes the flame. 
MICEOSCOPY. 
The Microscopical Socid'ifs Prizes. — Since our last issue, the meeting of the 
Council of the Microscopical Society, which was to have decided upon the 
merits of the instruments sent up for competition, has taken place. We 
regret to perceive that the result has been most unsatisfactory ; not only did 
none of the distinguished manufacturers send in microscopes for the Society’s 
medals, but even those who did forward instruments complain bitterly of the 
mode of adjudication. Certainly there must be something wrong somewhere ; 
either the makers consider that the Society’s medal is of no service as a 
guarantee to the public, or they consider that the judges are not as impartial 
in forming their decisions as they should be. It is not for us to say to which 
of these circumstances the result is due ; but the facts remain that the 
microscopes sent in for examination were, with one or two exceptions, those 
of manufacturers unknown to histologists, and that there has been a great 
deal of ambiguity concerning the exact nature of the decision of the Council. 
The p-Q- Inch Objective. — This, the wonder of all microscopists, has been 
manufactured by Messrs. Powell & Lealand for Dr. Lionel Beale. It is, 
without doubt, an exquisite glass, giving an extremely flat field and marvel- 
lous definition. Its angular aperture is smaller than the twenty-fifth inch of 
these makers, being 150°, and its price is thirty guineas. It w^as exhibited at 
the soiree of the President of the Royal Society on Saturday, March 11th, 
and the object displayed by it (the Podura’s scale) proved the extraordinaiy 
qualities of the new power, the markings appearing almost like distinct 
scales. Its magnifying power under the No. 1 eyepiece is 2,500 diameters ; 
but, by employing the 5th eyepiece, it may be brought up to 15,000 
diameters. When it is remembered that the lenses of this objective are 
themselves so small that the workman is obliged to use a microscope in pre- 
paring them, some idea may be formed of the difficulties attending their 
manufacture. 
The new Popular Microscope'^ of Messrs. Smith & Beck is a great 
improvement upon their “Universal” instrument, and bids fair to achieve 
popularity. It is intended for those who want a sound working instrument, 
not of the very highest finish, but at a moderate cost, and with all the 
