222 



SCIENCE. 



groupings more complex than those which give us the yel- 

 low and green lines. The visibility of the green lines, 

 which are short, in the flame, taken in connection with the 

 fact that the} - have' been seen alone in a vacuum tube, is 

 enough for my present purpose. 



With regard to the second point, the passage from the 

 heat-level of the flame to that of the spark after volatiliza- 

 tion is complete, produces no visible effect, indicating that 

 in all probability the effects heretofore ascribed to quantity 

 have been due to the presence of the molecular groupings 

 of greater complexity. The more there is to dissociate, the 

 more time is required to run through the series, and the better 

 the first stages are seen. — Nature. J. Norman LOCKYER. 



THE RICHMOND DIATOMACEOUS EARTH. 



The stratum of fossiliferous earth underlying the cities 

 of Richmond and Petersburg, in Virginia, when first dis- 

 covered by Prof. Wm B. Rogers, in 1842, was supposed to 

 be peculiar to those localities ; the further investigations of 

 geologists have shown it to be a material constituent in 

 various parts of the great Tertiary formation which bounds 

 the continents of North and South America, and, perhaps, 

 those of the Eastern Hemisphere also. To Mr. Charles 

 Stodder we are indebted for the interesting and suggestive 

 fact, that a stratum of infusorial earth, apparently tne same 

 as the Richmond deposit, has been struck at a depth of five 

 hundred feet at Fortress Monroe, in boring an Artesian 

 well. 



The deposit at Richmond has long been famous with 

 microgeologists for the great variety of beautiful forms it 

 contains ; the illustrious Ehrenberg having assigned to it 

 one hundred and twelve species — nearly double the num- 

 ber to be found at any other place on the Atlantic coast ; 

 and the subsequent researches of microscopists have shown 

 it to be perhaps the richest deposit of the kind in the 

 world, every new preparation of the earth revealing some 

 forms not before noticed, many of the most interesting re- 

 maining unnamed or described to the present day. The 

 stratum varies in thickness from twenty to forty feet, and 

 Major Bolton, engineer of the Church Hill tunnel, at Rich- 

 mond (which runs through the deposit for three-fourths of a 

 mile), informed me that at certain points of that excavation 

 it reached a maximum thickness of eighty feet. In addition 

 to an inexhaustible supply of the Diatomaceous earth, that 

 work brought to light thousands of fossil remains of the 

 gigantic marine monsters that, long ages ago, swam in the 

 deep ocean over the spot where the city now stands. 



An observation of the sections made by the various 

 water courses which cut through the plateau on which 

 Richmond is built, shows the deposit to be nearly level — 

 its upper surface about fifteen or twenty feet below the top 

 of the ground, and perhaps one hundred feet above tide- 

 water. The Petersburg deposit was regarded by Prof. 

 Tuomey as belonging to a different geologic era from that 

 at Richmond, as evinced by the fact of his finding the casts 

 of Pectens and other Meiocene fossils below that deposit, 

 while at Richmond they are found above. The great differ- 

 ence in the character of the two deposits would also indi- 

 cate this, the Petersburg Diatoms being generally much 

 more transparent than the Richmond forms, and differing 

 also materially in species. Upon exposure for sometime 

 to the weather, this earth assumes an almost snowy white- 

 ness, and crumbles to a fine powder, but as first dug from 

 the depths of the earth it resembles bituminous coal in 

 color and solidity — so tough and hard is it, that in remov- 

 ing it from the tunnel it was blasted with gunpowder just 

 as any Other rock. Its composition, as nearly as can be 

 estimated in a general way, is — 10 per cent, unbroken forms 

 of the DiatomaCX, 25 per cent, fine white sand, and the 

 balance fine clay, formed, perhaps, mostly of the decom- 

 posed ami broken Diatoms, the. whole mass interspersed 

 with many sponge spicules and a lew Polycistena, and so 

 strongly impregnated with alum that many of the wells and 

 springs in Richmond are injured by it. To the micros- 

 COpisI this deposit is a source of unfailing interest, 

 Whilst the most inexperienced in such matters, upon 

 being shown the wonderful forms found in it, are 

 strmk with Surprise and delight. Had the pre-historic 

 man possessed a microscope it might have been supposed 



that the forms seen in this deposit may have suggested the 

 forms of many of his appliances, as in it may be found 

 models of almost all the implements used by savages, 

 whether for war, the chase, or in domestic life ; witness, for 

 instance, his stone hatchets, arrow and spearheads, knotted 

 clubs, boomerangs, &c. ; a catalogue of such matters used 

 by civilized people would embrace plates, dishes, cups, 

 saucers, knives, forks, scissors, balls, tops, spectacles, 

 watches, anchors, dumb-bells, cannon, coin, musical notes 

 and many other articles ; the investigator being constantly 

 startled by the strange resemblance which hundreus of 

 these ancient natural forms bear to things in every 

 day use. Certain varieties, however, predominate, and 

 their distribution varies with level and locality, 

 the upper portion of the stratum being com- 

 paratively poor in forms, while they increase in 

 number and variety as we descend to the lower levels. The 

 genus Coscinodiscus seems to characterize this earth, and of 

 it there are dozens of varieties varying from the (microscop- 

 ically) enormous C. gigas to the minute and elegant C. 

 stelliges which resembles closely a finely polished opal, 

 requiring a lens of wide aperture and considerable power 

 to show its areolations. Orthosira marina is everywhere 

 abundant, whilst many beautiful forms of Navicula are 

 found in even- gathering. Amongst these we may specially 

 note two kinds of Pleurosigma, one of which, P. 

 angulatum, is a favorite test Diatom, and the other, 

 which it is is proposed to call P. Virginica, (as it is 

 the most common form of Pleurosigma in the Virginia 

 earths), is remarkable for the beauty of its contour, which 

 exactly copies a willow leaf, and the want of uniformity in 

 its striae, which are much coarser in the middle than at the 

 ends of the valves, It can be easily resolved with a good 

 }( in. Objective, without the aid of oblique light. The 

 genus Triceratium, is also well represented by many beau- 

 tiful varieties, the handsomest of which is, perhaps, T. 

 Maylandica, which can be resolved with almost the same 

 ease as P. Virginica, Isthmia enervis, Biddulphia Tuomeyii, 

 Terpsina? musica, Anlacodiscus crux, Navicula lyra, 

 Gonphonema, Heliopelta, Asterolampra Concinna, Aste- 

 romphalus, Brookeii, and Synedra, are more rarely met 

 with. 



From the great variety in the markings on these valves, a 

 slide of the earth, properly prepared, becomes one of the 

 best and most interesting tests for the performance of ob- 

 jectives, from the lowest to the highest powers in general 

 use. On some of them, for instance, the areolations may 

 be seen with a simple triplet, whilst on others a first-class 

 objective of wide angular aperture, aided by all the modern 

 refinements of illumination, is needed to show them. 



Mr. C. L. Peticolas, of 635 Eighth street, Richmond, Va., 

 has sent us for inspection a few of his recently mounted 

 slides of the Richmond earth, prepared by a new process for 

 separating the Diatom? from the extraneous matter. We 

 have pleasure in stating that these slides show the leading 

 characteristics of this deposit very clearly and beautifully. To 

 those who are studying these forms of fossil diatomacex, 

 the slides of Mr. Peticolas will be very acceptable, and 

 they should be added to the cabinet of all who possess a 

 good microscope. 



A useful list of the Longicorn beetles, or wood 

 borers, constituting the vast number of insecis injurious 

 to our forest, shade, and fruit trees, may be found in the 

 October number ot The American Entomologist, briefly 

 arranged in the order of their most recent classification. 



THERK are two beetles in the United States, both 

 commonly called " Fire-fiies ," which are now known to 

 be luminous in their larval as well as in their perfect 

 state; the one Thoturus Pensylvanica, De Oeer.the other 

 species Photurus pyralis, Linn. Both the males and 

 females of these species have wings, and therein they 

 differ from the true Glow Worm Of England {I.aniftyris 

 noctiluca), the female of which is wingless and emits a 

 much more brilliant light than does her winged mate. — 

 C. V. Riley. 



