SCIENCE-GOSSIP. 



269 



dritic formation are derived from the strata over- 

 laying the flints, or whether the cherty flints 

 contain the minerals in themselves. 



" In examining broken flints with a pocket-lens, 

 many, minute cavities can be seen, containing what 

 appears to be oxide of some 

 mineral, with small fragments 

 of Inoceramus and other chalk 

 fossils. After these freshly- 

 broken flints have been ex- 

 posed to the atmosphere for a 

 few days, oxides of minerals 

 appear on the freshly-fractured 

 surface. Flints thus treated 

 do not produce dendritic forma- 

 tions. To find this arbor- 

 escence we must with care 

 select likely-looking complete 

 specimens, and search with the 

 pocket-lens for signs of a very 

 fine fissure, so fine that it 

 would not contain the thinnest 

 gold leaf. Having discovered 

 such a fissure, experience in 

 using the hammer is necessary 

 to enable one to produce good 

 results. The flint being broken 



along a continued line of the fissure, the dendritic 

 formation is exhibited, in fac-simile, on both faces 

 of the old fracture which constituted the fissure. 



"The forms assumed are very varied indeed. 

 Some remind one of Arabic writing, This forma- 

 tion seems to overspread old dendrites that can 

 only be faintly seen, and which appear to have 

 become obliterated by age or exposure. A second 

 deposit or re- formation has taken place, hence the 

 Arabic-like characters. In other instances the den- 



Fractured Flint with 

 Mr. W. Gamble 



drites form quite a landscape picture, with fore- 

 ground, hills, valleys, and woodland in the distance. 

 These are very wonderful, and extremely beautiful. 

 " I have artificially produced dendritic patterns 

 on the clean surface of .fractured flints. The way 

 to proceed is to break the flint 

 with a hammer ; if they hap- 

 pen to have an even surface 

 place the two parts together 

 again. The space between 

 will differ very little from a 

 natural fracture or fissure pro- 

 duced by atmospheric influence. 

 Take another flint in which 

 there are oxides on the broken 

 surfaces. Wash these off with 

 water, which pour into the 

 clean fracture of your broken 

 flint, care being taken that 

 the parts fit closely. Now 

 bind with cord to prevent 

 the two parts moving. Then 

 place in the sun or a warm 

 oven until all the moisture is 

 dried out and disappeared. 

 Then separate the two parts, 

 and find the artificial den- 

 drites on both surfaces of the broken flint. It 

 is therefore certain that dendrites are produced 

 in a very short space of time, under proper 

 conditions." 



In his investigations of the dendrites on fractured 

 flints, the points on which Mr. Gamble would be 

 glad of information are whether these crystals are 

 of manganese ; if so, from whence does it come, 

 and what brings about the arborescent patterns in 

 crystalization ? 



Dendrites. From 

 s collection. 



ANIMAL HAIRS. 

 By John R. Lord. 



(Concluded from page 249 J 



(~\N examining with the microscope the hairs of 

 ^^^ different animals, they are found to present 

 different characteristics ; the size of the medulla, the 

 arrangement of the cells forming it, and the presence 

 of air within it, greatly tend to alter the microscopic 

 view of a hair. In the rodents the cortex seems to 

 send septa into the medulla, dividing it into a 

 multitude of compartments. Such is the appear- 

 ance when the septa are in a direct line with the 

 observer's eye, but if the septa are seen obliquely, 

 a chain-like appearance is produced (fig. 3 — e,f). 

 Occasionally very intricate and complicated patterns 

 are seen (fig. 3a), and some hairs seem to have very 

 little cortex, and a very wide medulla. A transverse 

 section of the hair of a pecari will show fibrous septa 

 radiating from a central pillar to the cortex. The 



hair of the bat is seen to have successive whorls 

 of pointed lance-like projections, like leaves without 

 stems ("Carpenter's Microscope," 3rd ed., p. 711). 

 The greater part of the surface of the human body 

 is covered with hair, but in certain positions it is 

 found in profusion. These very small hairs which 

 cover the body generally (lanugo), have no medulla. 

 Races of men are characterized by different kinds 

 of hair. The negro hair is oval in cut section, and 

 is placed in a curved follicle ; this is the reason of 

 its curly appearance. The English hair is not 

 quite circular in cut section, but the Japanese hair 

 is. Dr. Lathan disputes the existence of "black 

 hair" ; he says: " a negro's hair is black only when 

 the light falls straight upon it. When seen in a 

 cross light it has a red tinge — red, redish or brown ; 



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