58 



HARDWICKE'S SCIEXCE-GOSSIP. 



March 1, 1868. 



in this respect are those of our western coast. I 

 have now before me a block of pure diatomaceous 

 eartb, a foot and a half long by half a foot in depth, 

 of chalk-like whiteness, sent by Mr. W. P. Blake 

 from Monterey (the entire weight of which is only 

 about six pounds), and other similar beds are found 

 at many points in Mexico, California, aud Oregon. 

 One of these, discovered by Colonel Fremont on 

 the Columbia River, surpasses all other known de- 

 posits, being not less than 500 feet in thickness, and 

 covered by at least 100 feet of compact basalt and 

 other volcanic products. 



It is probable that the Mexican and Californian 

 beds, like those of Richmond, are of Tertiary age, 

 though some of them may prove to be Cretaceous. 

 That those of Monterey and San Praucisco are far 

 more ancient than the present physical features of 

 California, is proved by their beiug purely marine 

 deposits, and by their differing wholly in character 

 and species from other deposits, also of con- 

 siderable thickness, from the eastern side of the 

 Sierras, which I have lately had an opportunity of 

 examining. These latter are fluviatile or lacus- 

 trine, and contain many species identical with those 

 of the ordinary subpeat deposits of the Eastern 

 States. 



In passing from the Tertiary to earlier formations, 

 the evidence of the existence of the microscopic 

 Algae becomes less evident, and for a long time none 

 were believed to exist of more ancient date than 

 those above alluded to. Certain peculiar organisms 

 termed Xanthidis were, however, observed as of 

 frequent occurrence in the flint nodules of the chalk 

 formation, and within a still more recent period 

 similar forms have been observed in the analogous 

 horn-stones of the Devonian and Silurian ages, 

 associated in this latter case with unequivocal Dia- 

 tomaceous shells. As regards these Xanthidia, 

 which have usually been regarded as remains of 

 Desmids, it is certainly singular that, while all 

 recent Desmids are purely fresh-water, these should 

 occur in marine deposits ; and secondly, that, 

 destitute as they are for the most part of the sili- 

 ceous shell of the Diatoms, they should occur in a 

 fossil state at all. Yet the resemblance is certainly 

 a stricking one, and their occurrence with the kin- 

 dred Diatomacea: throws some degree of plausibility 

 upon this belief. However this may be, the exist- 

 ence of one group at least of these organisms being 

 established for these early periods, we can scarcely 

 doubt that their numbers were as great then as in 

 the seas of our own day, and that they have been 

 present through all the great geological ages, even 

 though metamorphism and other agencies have for 

 the most part obliterated all traces of their beautiful 

 but fragile shells. It is highly probable that accom- 

 panying the lower forms of animal life, these humble 

 types of vegetation were among the first introduced 

 upon the globe, performing then, as their repre- 



sentatives now do in the' arctic seas and at great 

 depths, where the higher forms of vegetation are 

 wanting, the part of purifying the waters, as well 

 as of contributing food for the sustenance of the 

 different forms of animal life with which they 

 were associated. — Professor Bailey, in "American 

 Naturalist" 



THE PLY1XG SPIDER. 



A MONG the hundred varieties of spiders, there 

 -^*- is but one of the real flying kind, although 

 the " cat spider," that always leaps on its prey, 

 instead of entangling it in his web, will sometimes 

 swing off by its thread, and various other kinds will 

 be blown from one tree to another, and weave their 

 gossamer with geometrical precision in mid-air 

 between them ; yet none of these indulge in balloon 

 voyages. 



The flying spider is a pale, light, ashy coloured 

 insect, or rather animal, and in this latitude thousands 

 of these little aeronauts may be seen every autumn, 

 vieing with each other in sailing the highest. They 

 seem to be chemists as well as mechanics. They 

 get themselves in a state somewhat like the silk- 

 worm before it begins winding its cocoon ; nearly 

 all that is inside of their bowels is formed' into 

 silken thread, and being thus rendered very light, 

 they wait for a fair day and gentle breeze, when by 

 hundreds and thousands, like birds of passage, they 

 undertake their airy journey. Firstly, they climb 

 upon some shrub, tree, or fence, where they stand 

 awhile with their legs directly under the body, and 

 to all appearance inflating themselves with gas, 

 until the back part of their bodies become semi- 

 pellucid. When fully ready, one does not wait for 

 another, but proceeds to attach its cord to the 

 object on which it is standing, then leaps up and 

 off, fearlessly giving its body to the breeze, gradually 

 rising like a kite until it reaches the end of its 

 string, being generally high up and out of sight. I 

 presume a moderate breeze would carry them a 

 long distance after their thread was broken. I 

 have seen them rise higher than the tallest trees, 

 and disappear in the blue ether, but I have never 

 failed to bring them down when suddenly cutting 

 their thread as soon as they had made their leap. 

 If, however, they rise twenty or thirty feet before 

 their thread is broken, they are safe, for the breeze 

 will carry them out of harm's way, though they 

 will then rise but slowly. Occasionally, after one 

 has started, another will run up his line with great 

 rapidity some fifteen or twenty feet before throwing 

 itself to the breeze. On the whole, it is both in- 

 teresting and entertaining to observe their move- 

 ments.—//. /. Eades, in the "Scientific American" 

 of Feb. 15, 1868. 



