Jan. 31, 1878] 



NATURE 



265 



I 



THE ORIGIN OF A LIMESTONE ROCK^ 



N November, 1845, I laid berore the Literary and 

 Philosophical Society of Manchester my memoir 

 "On some Microscopic Objects found in the Mud of the 

 Levant and other Deposits ; with Rennrks on the Mode of 

 Formation of Calcareous and Infusorial Siliceous Rocks," 

 which memoir was published in vol. vii. of the second 

 series of the Society's Transactions. In that memoir I 

 sought to demonstrate two things— ist, th it not only was 

 Chalk made up of microscopic organisms, chiefly Fora- 

 minifer^, as had recently been demonstrated by Ehren- 

 berg, but that the fact was equally true and explanatory 

 of the origin of all limestones except a few freshwater 

 Travertins ; 2nd, that some other extensive deposits, of 

 submarine origin, in which no Foraminifera could now be 

 detected, were not in the s'ate in which they were origi- 

 nally accumulated. I concluded that Foraminifera had 

 doubtless been present in them also, but that their cal- 

 careous shells had been dissolved out of them, and that 

 this d sippearance had been effected through the agency 

 of water containing carbonic acid, at an early stage of 

 the formation of these deposits. As is well known, this 

 latter theory h^s been reproduced as a new one by some 

 of the naturalists of the Challenger expedition, who have 

 applied it to the explanation of phenomena of a sub- 

 stantially similar nature to those which I endeavoured to 

 account for, in the same way, more than thirty years 

 previously. 



I am indebted for the slab of limestone forming the 

 subject of this communication to my fdends the Messrs. 

 Patteson, the marble merchants of Oxford Street, Man- 

 chester. This slab appears to illustrate in an exquisite 

 manner both the theories to which I have just referred. 

 It is a specimen of the BoUand limestone, which, when 

 sawn through, was found to contain a large concamerated 

 Nautiloid shell more than twelve inches in diameter, which 

 appears to me to have been a true Nautilus, though the 

 section has not passed exactly through its centre so as to 

 reveal any portion of its siphuncle. In the various parts 

 of this slab we find the calcareous material exhibiting 

 different conditions. Throughout the greater part of its 

 substance we have evidence that it has originated in an 

 accumulation of minute calcareous organisms — especially 

 Foraminifera— but most of these are disintegrated and 

 display vague outlines, a condition wh ch I presume has 

 resulted from the action of the carbonic acid already 

 alluded to. 



Scattered through the slab are numerous dark-coloured 

 patches of a substance apparently identical with what the 

 late Ur. Mantell designated MoUuskite, and which he 

 believed to be the remains of the sofc animal substance 

 of marine organisms. In many of these patches the 

 Foraminif rous shells are better preserved than is the case 

 with the rest cf the matrix inclosing the large fossil shell. 

 It appears as if this MoUuskite had partially protected 

 the cdlcareous Foraminifera from the solvent action which 

 had disintegrated most of those forming the rest of the 

 deposit. 



But the most interesting features of the specimen are 

 seen within the chambers of the Nautiloid shell. The 

 Foraminiferous ooze has entered freely through the large, 

 open mouth of the terminal chamber in which the animal 

 resided and filled the entire cavity of that chamber. 

 There is no doubt whatever as to the original identity in 

 the character of the ooze thus inclosed within the shell 

 and that which constitutes its investing matrix, though 

 they now appear very different. The latter portion was 

 freely permeated by water containing the solvent carbonic 

 acid ; hence the more or less completii disintegration of 

 its Foraminiferous shells. But in the limestone inclosed 



I "Onihe Microscopic Conditions of a Slab Tnin the Mountain Lime- 

 stone of BollanH," by W. C. Williamson, K.R S.. Prufessor of Natural His- 

 tory in Owens College. Read before the Literary and Philosophical 

 Society o: Manchester, January 8. 



within the large terminal chamber of the Nautiloid shell 

 almost every Forammifer is preserved in the most exqui- 

 site perfection. This is especially the case in the deeper 

 part of the chamber, most remote from the mouth, as also 

 in the instances of one or two of the more internal closed 

 chambers, into which the mud has obtained entrance 

 through small accidental fractures in the outer shellwall. 

 It appears obvious to me that the thick calcareous shell 

 of the Nautilus has protected the inclosed shells of the 

 Foraminifera from the action of the solvent acid. I repeat 

 that there is no room whatever for doubting that both 

 portions of the Foraminiferous ooze, whether contained 

 within or surrounding the Nautiloid shell, were originally 

 in identical states. Microscopic observation makes this 

 sufficiently plain. The differences now observable be- 

 tween them have arisen from changes which have taken 

 place subsequent to their primary accumulation, and which 

 changes have been due to differences of position ; the one 

 portion has been protected by the thick calcareous Nauti- 

 loid shell which would rob the water percolating through 

 it of all its solvent carbonic acid, and thus preserve the 

 contained Protozoa from destruction, and which pro- 

 tection would continue so long as any portion of the 

 Nautiloid shellwall remained undissolved. The other, 

 being unprotected, would be exposed to the full action of 

 the solvent, which would percolate readily amongst the 

 loosely aggregated microscopic organisms, and speedily 

 act upon their fragile shells. 



But there is a yet further feature in this interesting 

 specimen requiring notice. The closed chambers of the 

 Nautiloid shell are all filled with clear, crystalUne, cal- 

 careous spar. The aciduUted water, acting upon the 

 calcareous Foraminifera of the ooze has become converted 

 into a more or less saturated solution of carbonate of 

 lime. This has passed, by percolation, through the shell 

 of the Nautilus into its hollow chambers. Finding there 

 suitable cavities it has gradually filled them up with a 

 crystalline formation of calcareous spar, and which of 

 course exhibits no traces of the minute organisms from 

 which the calcareous matter was primarily derived. A 

 similar crystallisation has filled up the smaller interspaces 

 between the Foraminiferous atoms both inclosed within, 

 and external to, the Nautilus, rendering the limestone 

 capable of receiving a high polish. 



If these explanations are as correct as I believe them 

 to be, we have here the entire history of the origin of a 

 limestone rock — from the first accumulation of the Fora- 

 miniferous ooze, as seen in the interior of the first large 

 chamber of the Nautilus, to the deposition, in an inor- 

 ganic mineral form, of the crystallised carbonate of lime 

 within the closed chambers of the Nautilus, all being 

 illustrated within the area of a slab of limestone little 

 more than a foot in diameter. 



THE LIQUEFACTION OF THE GASES 



IN the recent article, in which the magnificent results 

 recently obtained by MM. Cailletet and Pictet were 

 detailed, we contented ourselves, in the account of the 

 methods employed, by pointing out the extreme sim- 

 plicity of that used by M. Cailletet. The 'simplicity, 

 however, by no means takes away from the beauty of the 

 method, and we now propose to return to it with a view 

 of showing how closely it resembles in many of its 

 details that employed by Dr. Andrews in his classical 

 work on the continuity of the various states of matter. 



Dr. Andrews, it will be remembered, in his experiments 

 on the liquefaction of carbonic acid, used a glass tube 

 capillary in the upper part, and in the remainder, of a 

 bore just so wide that a column of mercury would remain 

 in it when the tube was held in a vertical position. The 

 gas to be operated on was confined to the narrow upper 

 part of the tube by mercury, and the tube was tightly 

 packed to an end piece of brass armed with a flange. 



