10 



HARDWICKE'S SCIENCE-GOSSIP. 



[Jan. 1, 1S67. 



which is to be allowed to settle, and the water then 

 poured off and the sediment transferred to an oil- 

 flask (which has been well cleaned), and boiled with 

 nitric acid over a candle, or gas jet. After the first 

 portion of acid ceases to act, the flask, with its con- 

 tents, must be set aside till the liquid is perfectly- 

 clear, when it is to be poured off, and fresh acid 

 added. This is to be continued as long as the acid 

 exerts any action, and the sediment is perfectly 

 white, when it is to be washed with water until the 

 liquid is no longer acid. 



In this sediment, when examined by the microscope, 

 maybe found the Triceratiumfavus,whichis oneof the 

 largest of the Diatomacese, and is about the rib-th of 

 an inch in diameter. It is in the form of an equilateral 

 triangle, with slightly curved sides. At each comer 

 is a projecting spine or hook, and round the base of 

 each there is a row of round dots ; and the rest of 

 the surface is covered with large and regular hexa- 

 gonal markings, resembling, in the closest manner, 

 the formation of honeycomb. If you wish to mount 

 it, when found, you must pick it out from among 

 the grains of sand and other impurities by the help 

 of a stout hair from a shaving-brush, or a cat's 

 whisker stuck in a split at the end of a slender 

 wooden handle, such as a paint-brush handle, and 

 place it in the centre of a glass slide. A drop of 

 Canada balsam is then to be added, and the slide 

 warmed till the balsam becomes rather hard. On 

 cooling, all the air-bubbles should be broken by the 

 point of a needle, and then the thin glass cover is 

 to be put on, taking care to have the object as nearly 

 in the centre as possible, and not to press so hard as 

 to break it. Objects mounted in this way, under 

 small round pieces of thin glass, on plain ground- 

 edged slides, look very neat ; and all the rest of the 

 things described in this paper may be mounted in 

 the same way, though more than one specimen may 

 be mounted at once. Surirella constricta, which 

 resembles a lady's needle-case, may also be found. 

 It has strongly-marked ribs running from the out- 

 side edge towards the centre, where a clear space 

 may be observed. Surirella plicata has no resem- 

 blance to the last ; but strongly resembles a lemon 

 in outline, as does also another object (of which I 

 never found but one), but which is covered with 

 minute dots instead of being marked with faint lines. 

 A small but beautiful variety of the Cosci/wdiscus, 

 which is a round shell resembling a thick shilling, 

 closely covered with dots on both sides, is worth 

 mounting, when found ; but, being extremely brittle, 

 great care must be used. The Gramataphora ser- 

 pentina is found in great numbers, and is like a card- 

 case, with four curved lines running from opposite 

 ends towards the centre. Different kinds of Navi- 

 culee, or little ships, are to be found by careful 

 examination ; and they arc very amusing when alive, 

 for they run about and bump up against one another, 

 then draw back after a time and swim away in the 



opposite direction. A few specimens of Pleurosigma 

 hippocampus (Sea-horse), and some other varieties 

 of these most beautiful objects, which are at once 

 recognized by their form, which is that of Hogarth's 

 lines of beauty of different curvature joining at 

 their ends, and having another which runs between 

 them and expands in the centre, and at each end 

 into round dots or spaces (which some say are open- 

 ings : others, only a thickening of the central rib ; 

 but I am inclined to believe the latter, from the 

 manner in which the valve is broken on being 

 pressed ; for the crack does not run across the dots, 

 as it would do if they were openings, but round 

 them, proving them to be stronger there than else- 

 where) . And all the rest of the surface is covered 

 with rows of minute dots, arranged in regular rows, 

 but so fine that, except with the very highest powers, 

 nothing can be seen but longitudinal and transverse 

 lines; and a i-inch that will show even these may 

 be considered very good. 



JPimularia dactylus is like Surirella constricta, 

 only much smaller and expanded instead of con- 

 tracted in the centre. The Gallionela sulcata is 

 a beautiful object, and resembles highly-carved 

 ivory bones stuck end to end, so as sometimes to 

 form a filament appearing as much as three inches 

 in length, when viewed under a good \ inch power. 

 Symphonema geminatum, which may be compared to a 

 number of folded fans attached to a branched stalk 

 by the end held in the hand; and Acnanthes 

 longipes, which is a bundle of oblong boxes joined 

 together and connected by a long gelatinous stalk 

 to the weed, complete the list of those from South- 

 end which I have found ; but I have no doubt that 

 a much greater variety would be obtained if the 

 weeds were collected at the proper time. 



A great number of the most beautiful forms are 

 contained in fossil earth, which may be obtained 

 from dealers in minerals. Those of Bermuda, Oran 

 in Algeria, and Richmond, U.S., are the most 

 important, and contain the greatest variety. 

 Bermuda earth contains one most beautiful object, 

 the Heliopelta (sun-shield), of which a tolerable 

 notion may be got s by cutting an orange in half 

 transversely. Then every alternate triangle you 

 must suppose to be marked with a different pat- 

 tern — one being covered with large and regular 

 round markings ; and the next, which appears to be 

 on a different level, to be marked with smaller and 

 less distinct, but nevertheless very beautiful mark- 

 ings. The ribs which divide the triangles from one 

 another, dilate at their extremities, forming in the 

 centre a clear space corresponding to the central 

 pith in the orange, and at the ends next the margin 

 expand and gradually melt into the rim or border, 

 which is thickly set round with transparent spikes 

 of different lengths. The earth from Richmond 

 affords many beautiful specimens, especially of the 

 genus Nacicula. 



