ON MICROSCOPIC DISCOVERY. 



593 



mon operation of striking fire from flint and 

 steel. 



' ; In the common way of striking fire with 

 a flint and steel, fiery sparks fly out at every 

 blow ; which sparks are nothing more than 

 small pieces of the flint or steel, (but usually 

 of the steel) broken off by the violence of the 

 stroke, and either melted instantaneously into 

 steel globules, or made at least red hot, and 

 thereby capable of kindling tinder or touch- 

 wood. The heat is likewise so intense as 

 sometimes even to vitrify the broken particles. 

 Dr Hooke struck fire over a sheet of very 

 white paper, and observing diligently where 

 the sparks seemed to vanish, he discovered 

 there certain very small, black, but glittering 

 and movable specks, which when examined 

 with his microscope, appeared to be little round 

 globules; some whereof did, from their sur- 

 face, yield a very bright and strong reflection 

 on that side next the light, and resembled iron 

 balls. The melting of the particles of steel, 

 instantaneously, upon the collision, is very 

 wonderful, and comes up nearly to the effects 

 of lightning.'' The combustible nature of iron 

 and steel is evidenced by the simple experi- 

 ment of letting drop the filings of either 

 through the flame of a candle, when a num- 

 ber of the particles will be found melted into 

 small globules. On burning a red wafer over 

 a piece of glass, and submitting the latter to 

 the microscope, several very regularly formed 

 globules of lead will be discovered. 



We must now glance at the minute petri- 

 factions, and fossil remains, of marine animals, 

 insects, animalcules and vegetables; and this 

 division of our subject will bring before us 

 startling discoveries, to which the mind is 

 scarcely disposed to give credence. A little 

 reflection, however, upon the mighty opera- 

 tions which are continually going forward in 

 the microscopic world, will lead us to appre- 

 hend so much of these wonders as is necessary 

 to excite our belief in them. We shall of 

 course be understood to refer to the infusorial 

 organic remains discovered by Ehrenbef^. 



Referring to the remains of marine animals, 

 Mr Pritchard has the following observations, 

 in his Microscopic Illustrations, p. 20 : *' Look 

 at the discoveries of Agassiz on the fossil crea- 

 tures of the deep! By a microscopic investi- 

 gation of such portions of them as have with- 

 stood the destructive power of time, namely, 

 their scaly covering, he has been able so to 

 group and class them, that the characters and 

 habits of the genera belonging to each distinct 

 era are clearly demonstrated. A microscopic 

 examination also of the testaceous remains of 

 sundry Entomostraceans, found in slate-clay 

 formations, now elevated much above the le- 

 vel of the sea, prove them to have been at some 

 time or other imbedded in the Waters. And 



the naturalist may even determine by an in- 

 spection of the shell, whether the species were 

 the inhabitants of fresh or salt water, and con- 

 sequently whether the strata themselves were 

 the indurated beds of the sea, or of some river 

 or lake." 



Fossil remains of insects have hitherto 

 rarely been met. with ; and of those which 

 have been discovered very few are satisfacto- 

 rily developed by the microscope. Blumenbach 

 divides them into three sections. 



I. " The Determinable ; such for instance as 

 those found in the schist at Oeningen, larvas 

 of Libellulee, Notonectas, &c. II. Dubious; 

 to which head belong most of those inclosed in 

 amber, as also most of the petrified crabs. 

 III. Unknown; such are the celebrated Dudley- 

 fossils, which are found in various places, but 

 no where finer than at Dudley, in Worcester, 

 shire, and frequently retaining their crab-like 

 shell." Plate 4, figs. 39,40,41,42,43, 50,95, 

 represent a few of the insects that have been 

 discovered in a fossil state ; as these are par- 

 ticularly noticed in the general summary of 

 organic remains, it would be needless repeti- 

 tion to describe them here. Plate 35, fig. 41, 

 exhibits a singular insect, much resembling a 

 mite, discovered in a siliceous formation at 

 Uckfield in Sussex. It is drawn with nearly 

 four times the surface it exhibited under a 

 doublet of one thirtieth inch focus. Its real 

 size seems to vary from 1 -3000th to 1-1 500th 

 of an inch in diameter. 



The recent discovery of animalcular fos- 

 sils by Dr Ehrenberg of Berlin, has caused a 

 great sensation in the philosophical world, and 

 promises to aid in no small degree the ad- 

 vancement of geological science. " These re- 

 mains," says Sir David Brewster,"are the si- 

 liceous shells of animalcules belonging to the 

 division Bacillaria, and form strata of tripoli, 

 or poli-schiefer (polishing-slate), at Franzen- 

 bad, in Bohemia. M. Ehrenberg has still 

 more recently discovered them in the semi- 

 opal found along with the polishing-slate in 

 the tertiary strata of Belin, in the chalk flints, 

 and even in the semi-opal or noble opal, of the 

 porphyritic rocks. The size of a single indi- 

 vidual of these animals is about l-288th of 

 a line, or l-3456th of an inch. In the po- 

 lishing slate from Belin, in which there ap- 

 pear to be no vacuities, a cubic line contains, in 

 round numbers, 23 millions of these animals, 

 and a ci.bic inch contains 41,000 millions of 

 them. The weight of a cubic inch of the po- 

 lishing-slate is 270 grains. There are, there- 

 fore, 187 millions of these animals in a single 

 grain, or the siliceous covering of one of these 

 animals weighs the 187th millionth part of a 

 grain !" 



We anticipate the questions which will 

 arise on a perusal of this brief statement: 



