HARDVVICKE'S SCIENCE-GOSSIP. 



113 



■of obtaining pure arabin from ordinary gum- 

 arabic, which should be selected as clear and white 

 as possible. "This is to be dissolved in distilled 

 water to the consistence of thin mucilage. It should 

 then be filtered, and the filtrate poured into rectified 

 alcohol, and well shaken. The arabin immediately 

 separates as a white pasty mass, and the whole 

 becomes semi-solid. It must be placed on filter- 

 paper, and washed with alcohol, until the washings 

 are perfectly free from water, and the alcohol comes 

 off as pure as it went on. The arabin may now be 

 allowed to dry spontaneously. The edges of the 

 surface of the mass will probably be found to be 

 viscid, owing to the absorption of water from the 

 atmosphere or from alcohol, but the remainder will 

 be a perfectly pure white powder. This should be 

 shaken off the filter and preserved." 



DiATOMACE^ IN CoAL. — Professor W. C. William- 

 son, F.R.S., in his paper " On the Organization of the 

 Fossil Plants of the Coal Measures," has the following 

 remarks on Count Castracane's supposed discovery of 

 diatoms in coal. "This discovery, if real, was 

 valuable, hence its verification or the reverse became 

 desirable. My colleague. Professor Roscoe, kindly 

 allowed Mr. Smith, one of his able assistants, to sub- 

 ject numerous specimens of coal to Count Castracane's 

 process. The coals thus experimented upon were the 

 following Yorkshire and Lancashire ones — Bradford, 

 Worseley (16 samples), Middleton, Yorkshire (4 sam- 

 ples) Australia (3 samples). The result of these 

 investigations was to obtain a series of preparations 

 of a very diversified character, but in no one example 

 did I discover the smallest fragment of a diatom. 

 Mr. F. Kitton, of Norwich, informs me that he had 

 also examined many samples of coals from Durham 

 and Newcastle as well as from inland collieries, but 

 did not find a trace of a diatom. My friend the Rev. 

 E. O'Meara of Hazelhatch, Dublin, says he has 

 examined specimens of coal from Whitehaven, but 

 could not find any diatoms ; he also informed me 

 that the Rev. G. Davidson, of Logic Coldstone, 

 Aberdeen, had also examined a series of coals with 

 the same negative results. I can only conclude that 

 Count Castracane has been mistaken as to the source 

 of his diatoms." — Philosophical Transaclions of the 

 Royal Society, 18S0, vol. clxx. part ii. p. 519. 



Microscopical Society of Liverpool. — At a 

 recent meeting of this society, Air. Mayall, jun., 

 F.R.M.S., gave a paper on " Brass and Glass." Mr. 

 Mayall said it might be in the recollection of many 

 then present that about a year ago he had the honour 

 of addressing a few remarks to the Society on the 

 subject of immersion objectives, with particular refer- 

 ence to the increase of aperture which the immersion 

 system developed over the maximum apertures of dry 

 objectives. By " Brass and Glass " must be under- 

 stood that part of microscopy concerned with the 

 development of the microscope as an instrument, apart 



from its applications to this or that special branch of 

 study. Mr. Mayall said that it had recently been 

 most ungenerously stated in public that the "Brass 

 and Glass " party among the microscopists cared for 

 nothing but the mere display of elaborate apparatus, 

 that they vied with each other in encouraging the 

 manufacture of more and more expensive instruments 

 for the gratification of their personal whims and 

 fancies, and without the slightest reference to advanc- 

 ing any scientific branch of microscopy. It was no 

 part of his programme to explain in detail what 

 really was expected to be gained by encouraging 

 opticians to construct stands, objectives, condensers, 

 &c., which from their elaboration must necessarily 

 be costly, but might point generally to the fact that 

 the most conspicuous developments in recent micro- 

 scopy — particularly the delineation of microscopic 

 objects by means of microphotography — were 

 absolutely dependent on the perfection of the instru- 

 ment. Now the improvement of the instrument itself 

 was by no means so " petty " a subject as it had been 

 sought to insinuate; he (Mr. Mayall) thought that a 

 thorough investigation of the principles upon which 

 the improvement of the instrument depended was 

 by no means an unworthy or idle task ; and he 

 thought that if those principles were more generally 

 appreciated, much more rapid strides would be made, 

 and certainly there would be far less publicity given 

 to crude and erroneous interpretations, the ground, 

 would in fact, be cleared of much mere controversial 

 verbiage. Taking as an example the prevalence of 

 erroneous views with regard to the meaning and 

 function of aperture he would endeavour to lay before 

 the meeting a clear statement of the old theory of this 

 matter, and meet it point for point by the newer 

 views of which Professor Abbe of the University of 

 Jena was the originator. Then by means of a large 

 number of diagrams which he drew on the blackboard 

 illustrating his subject, Mr. Mayall dealt at consider- 

 able length on the main features of what he termed 

 the "aperture controversy," concluding his remarks 

 on that branch by an earnest appeal to all present if 

 they had any difficulties to suggest, to suggest them 

 forthwith, as it was the ardent desire of himself and 

 those with whom he was associated in the controversy 

 to have every point of difference thoroughly explained, 

 their sole motive being the promulgation of accurate 

 views. Mr. Mayall also exhibited and described in 

 detail several specimens of " Brass and Glass," some 

 of which he commended to the notice of the meeting. 



Weasel or Stoat ? — Will any of the readers o^ 

 Science-Gossip kindly inform me if the animal 

 usually known as the weasel, in the North of Ireland, 

 is properly so-called ? I read some years ago in a 

 work on natural history that it is the stoat, but have 

 no opportunity of verifying the statement from my 

 own observation. — y . IT. If. 



