H4 Progress in Physks. [January, 



passed through arrangements of intersecting glass rods, spun glass, and other 

 substances, and endeavours to explain the phenomena of the podura and other 

 unknown markings by reference to the curious appearances so produced. Mr. 

 Slack, as an example of deceptive appearances, cites an instance of minute 

 cracks in a film of silica, which when focussed in the manner most satisfactory 

 to the eye resemble tubes instead of fissures in the thin layer of silica.* 

 Professor Huxley considers that, at present, we have arrived at the end of our 

 optical resources, so far as histology is concerned, and does not believe that more 

 can be seen by the aid of a i-50th than with Ross's i-i2th. Dr. Beale invites 

 Professor Huxley, or other skilled microscopist, to examine a preparation to be 

 made by himself, first with a i-i2th or i-i6th, and to make a careful drawing 

 of all that he can discover, and afterwards to continue the observation with a 

 i-25th or i-50th, and then to decide whether these higher powers do or do not 

 reveal new structural details. Prolonged as the controversy will be, there can 

 be but little doubt that it will ultimately tend to the further improvement of the 

 microscope, by showing where high power definition is defective, and pointing 

 to the means of eliminating errors which possibly may exist even in the best of 

 our present objectives. 



Referring to the notice in a recent number of this journal, of the remarkable 

 magnifying power of 100,000 diameters having been obtained by a New York 

 pseudo-microscopist, an American correspondent says, " It was done by eye- 

 piecing and you know what that amounts to. But it was said that with this 

 power they photographed the Pleurosigma angulatum, showing dots two inches 

 in diameter. This is hardly a correct statement. Looking at the angulatum 

 through their microscopes, they made drawings of what they thought they saw ; 

 then made a pine model and photographed that ! It was all done to advance 

 the interests of a well-known manufacturer of cheap microscopes, but the 

 parties have no scientific reputation with us. The photograph is now on exhi- 

 bition in this country, but the true fads (which were related to me by one of 

 the assistants who knew the facts but did not appreciate the rascality) are not 

 generally known." As we have had no means of judging for ourselves, or of 

 making the necessary examinations, we do not accept the responsibility of our 

 correspondent's statements, but merely quote them from his letter. 



The death is announced of the President of the Royal Microscopical Society, 

 the Rev. Joseph Bancroft Reade, M.A., F.R.S. The deceased was one of the 

 founders of the society, also the author of many improvements connected with 

 the microscope and microscopical research, and also a Fellow of the Royal 

 Astronomical and Meteorological Societies. 



HEAT. 



M. G. Salet has described some peculiarities of the blue flame of sulphur 

 and some of its compounds. This blue flame is not hotter than red-hot iron, 

 and contains reduced sulphur ; but, at the perisphere of the flame, very 

 active oxidation takes place, and sulphuric acid is formed. By the same 

 arrangement the author has shown that the zone of aqueous vapour which en- 

 velopes the flame of burning hydrogen, contains nitric acid and binoxide of 

 hydrogen. 



M. Toselli, the inventor of a very ingenious ice-making machine, states 

 that experience has proved that ice made by his process withstands the influ- 

 ence of* a high temperature better than natural ice, or than any other ice 

 obtained by artificial means. To illustrate this fact, he adduces the instance 

 that a block of ice weighing 20 kilos., made by the author's process in 

 18 minutes, and sent off from Paris to Algiers on the 30th of June last, arrived, 

 properly packed, at its destination late in the afternoon of the 5th of July, the 

 block of ice then remaining still weighing 10 kilos. The loss, by fusion, on a 

 journey through a warm climate in the middle of summer was, therefore, only 

 84 grms. per hour. 100 kilos, of ice made by the author's process would require, 

 under the same conditions of temperature, 49^ days to liquefy it ; whereas 



* A specimen in illustration was exhibited at the November meeting of the Royal Microscopical 

 Society. 



