80 FORMATION OF STALACTITES— MERRILL. 



VOL. XVII. 



It is probable tliat the various forms of distortion and departure 

 from the straight tubular forms are to be accounted for in several 

 ways. An examination of the Medusa-like forms ot Wyandotte reveals 

 the fact that they occur not as dependents from the naked limestone of 

 the roof, but are offshoots from a stalactitic crust which forms first, and 

 which varies from a mere film to several inches in thickness. They 

 occur sometimes singly, but more connnonly in groups, or clusters of 

 several, ranging in sizes from 3 to 10 mm. in diameter. Closer inspec- 

 tion reveals the fact that while in most cases tubular, the tube itself is 

 of almost microscopic proportions, being as a rule less than half a mil- 

 limeter in diameter. So small is it, in fact, that capillarity, not gravity, 

 is the controlling principle in giving direction to the lime-carrying solu- 

 tion, A small spicule of calcite crystalizing on the extrendty is as 

 likely to point any other direction as downward: the direction of the 

 next drop is controlled in i)art by the first, where the same process is 

 repeated. Or on the assumption that the stalactite increases in length 

 by constant additions to the tube, on all sides, it is easy to imagine 

 that the deposit takes place, for a time, more rapidly on one side than 

 on the other, perhaps partially closing the orifice or giving it a differ- 

 ent direction. The essential fact is, hoAvever, that it is to capillarity, 

 and not to gravity, that is due the peculiar vermicular forms. Why, 

 at the outset, the stalactite should begin to form through many small 

 capillary tubes rather than through one larger, as is ordinarily the . 

 case, I will not pretend to say. It is to be noted, however, that in 

 Wyandotte, the roof forming limestones are neaily horizontal, while in 

 Luray and many other caves they are highly tilted. This results in a 

 more even percolation of the water in the first instance, the roof being 

 more homogeneous. It is possible, therefore, that the water gathers in 

 drops of smaller size, and very likely in smaller amounts. I have no 

 other than hypothetical data for this last assumption, however. 



The peculiar warty and distorted forms shown on pi. ill, from Luray, 

 I believe to be also due to the action of capillarity. In this case, how- 

 ever, the side excrescences are of secondary growth, the stalactite 

 having first formed, in part at least, in the ordinary way. Through a 

 closing of the tube at the lower extremity, the water either oozed 

 through the wall or perhaps ran down over the outer side until some 

 slight irregularity being met, it paused long enough for the necessary 

 precipitation to take place. Such forms are, in brief, but '^tricks of 

 crystallization" due to capillarity. 



Gypsum incrustations and rosettes. — As is well known, Wyandotte and 

 Mammoth Oaves yield in their older, dry, chambers, not stalactites of 

 carbonate of lime, but incrustations of gypsum in botryoidal masses, 

 acicular. crystals, and sometimes in the form of beautiful snow-Avhite 

 rosettes composed either of thin blades or acicular crystals of gypsum 

 grouped around a common center and curving outward. The appear- 

 ance and structure of characteristic forms may be best understood by 



