SCIENCE-GOSSIP. 



Note. — Mr. J. H. Cooke is obliged, on account 

 of increasing professional work, and for other 

 reasons, to discontinue conducting the department 

 of Microscopy in Science-Gossip. We lose his 

 assistance with much regret ; but are glad to 

 inform our readers that he will continue to be an 

 occasional contributor to our pages. — Ed. S.-G. 



Departmental Editor for Microscopy 

 Wanted. — The Editor of Science-Gossip will 

 be pleased to hear from any gentleman who is 

 willing to take the post of Honorary Editor of the 

 Microscopy Department in Science-Gossip. The 

 Editor will explain details on communication by 

 letter to no, Strand, London, W.C. One living 

 in or near London would be preferred, though that 

 is not a necessary qualification. 



Flotation of Foraminifera. — I am glad that 

 my note on this subject has elicited a reply from 

 so experienced a mounter as Mr. Earland (ante 

 p. 237). At the same time, there are several 

 points I should like to raise and questions I would 

 ask him. I am not quite convinced, foe example, 

 that the flotation method, which he admits will 

 only separate the lighter forams, is not somewhat 

 on the same footing as the coal sectioning nos- 

 trums which will only work with certain kinds 

 of lignite. If I have laid rather great stress on the 

 difficulties introduced by "capillary attraction," 

 it is surely desirable that these difficulties should 

 be taken into account instead of being ignored, 

 as is the case with most writers. I cannot claim a 

 very extended experience of the flotation method, 

 as all but one of my attempts have ended in 

 failures owing to this very cause. Some eighteen 

 years ago I received from correspondents packets 

 containing from a quarter of an ounce to one ounce 

 of sands from Leghorn and sponge sands from 

 Turkey and other localities, and though there 

 were plenty of Foraminifera to be picked out 

 by hand from them I found that when thrown 

 into water the floating portion contained, 

 apparently, quite as large a proportion of 

 sand as that which sank. Some pound or 

 so of sands collected at Margate, Woolacombe 

 and other localities give the same results, and 

 after wasting many hours at different times in 

 endeavouring to obtain even a small pinch of 

 flotsam containing sufficient Foraminifera to allow 

 of spread slides being mounted, I gave up Fora- 

 minifera as hopeless, and took to diatoms, as 

 being easier to clean. Quite lately the use of the 

 paper funnel, mentioned in my note, suggested 

 itself to me, and I tried it on some Colwyn Bay 

 sand. Seeing that the quantity at first used was 

 not very large, the " small pinch " of nearly pure 

 floated material can hardly be said to have been 

 unsatisfactory, although a second attempt with 

 rather more material yielded less Foramini- 

 fera. My next attempt was on some of the 

 Mediterranean sponge sand, and here I found 



flotation a complete failure. When introduced 

 through the paper funnel, this sand would carry 

 down a sausage-like cylinder of entrained air, and 

 when the bubbles rose to the surface and burst, the 

 fine sand would cling to the surface film with far 

 more tenacity than the Foraminifera. It is thus 

 evident that however successful flotation may be 

 in experienced hands, working with certain classes 

 of material, the scrappy directions given in books 

 are calculated to mislead a beginner. The omission 

 of any reference to this "capillarity" difficulty is 

 one of the chief causes of failure. I should be very 

 grateful if Mr. Earland would kindly give us the 

 benefit of his experience on the following points : 

 (1) Whether he has succeeded in separating 

 Foraminifera from this Mediterranean sponge sand 

 by flotation, and, if so, what precautions are neces- 

 sary ? (2) Whether this can be done successfully 

 with the small quantities that one commonly 

 obtains in exchanging, so that the yield, however 

 small, may be free from sand ? (3) Whether in work- 

 ing with larger quantities of material he experiences 

 any difficulty owing to the Foraminifera being car- 

 ried down and covered up by the descending sand- 

 grains ? If so, how can this loss be minimised by 

 properly choosing the size and shape of the vessel in 

 relation to the quantity of sand operated on ? — (Dr.) 

 G. H. Bryan (F.R.S.), University College, Bangor. 



Human Pediculi. — Mounted by the following 

 method human body-lice form most interesting 

 objects. Wash thoroughly with water, place 

 under a cover-glass with water, and press out the 

 blood which they generally contain. Clean again 

 with water and a camel-hair brush. Lightly dry 

 with blotting-paper, and mount at once in Farrant's 

 medium. The object thus prepared, viewed either 

 as a transparent or an opaque object, shows the 

 trached system most beautifully, even to the tiniest 

 branch. On no account should Canada balsam be 

 used as a mountant. By making acquaintance with 

 the officials at a workhouse, any amount of material 

 can as a rule be obtained. — Frederick Noad Clark, 

 Paddington Infirmary, Harrow Road, London, W. 



A Good Cement Varnish. — A thoroughly satis- 

 factory cement varnish may be manufactured as 

 follows with great ease. Two solutions are first 

 made, viz., a small quantity of Canada balsam and 

 an equally small quantity of storax balsam are 

 dissolved together in a little benzene, and again 

 some shellac is dissolved in alcohol. It may be 

 observed that shellac is almost insoluble in ben- 

 zene, while neither of the balsams mentioned are 

 quite soluble in rectified alcohol. However, on 

 mixing about one volume of the balsam solution 

 with about three volumes of the shellac solution, 

 the shellac is precipitated in a very fine state of 

 division. On using the mixture, it is shaken up 

 and applied with a small brush to> the edges of a 

 balsam or dammar-mounted preparation. At first 

 it seems muddy, but in a few minutes it dries on 

 the edge of the thin cover and becomes quite clear. 

 This varnish never gets too hard or tacky, and, as 

 far as I am aware, does not crack and is extremely 

 durable. Two or three coats applied is sufficient 

 to cement the thin cover firmly on to the slide, and 

 the whole may be finished with zinc white cement 

 and decorated with black or blue rings, etc. I 

 would earnestly entreat all microscopists to banish 

 gold size and asphalt varnish from their cabinets. 

 Some French and German microscopical works 

 barely mention these two articles, and they add 

 that "they are much employed in England." — 

 (Dr.) P. Q. Keegan, Patterdah, Westmorland. 



