1845.] 



THE CIVIL ENGINEER AND ARCHITECrS JOURNAL 



229 



gists must hail the microscope with joy. Dr. Carpenter has stated that 

 species mi;;ht be (letermincd liy tliis theory. In his (Dr. IJucklnml's) Bridge- 

 water treatise he had approached somewhat near to it, for he lad there ex- 

 hibited patterns which all resembled each other when belonging to the same 

 species, lie entirely agreed with Professor Sedgwick in his enconiinm on 

 the skill and ability with which Dr. Carpenter had conducted this important 

 inTestigatiou. 



Power of Laud Snails iofonn Holes in Roclis. 



Dr. linrkland said he had now to lay before the meeting the result of bis 

 investigation " On the agency of land snails in forming holes in compact 

 rocks." He was now convinced that by means of an acid with which they 

 ■were provided snails could make perforations upon the most solid forms of 

 limestone. He bad been often asked wliy, if this he true, tbi-y do not find 

 ■where snails were abundant that they had holes like mice. Now be had 

 been enabled to get at something like the rapidity at which these creatures 

 worked, and he now felt assured that when a hole was found two or three 

 inches deep, it had two or three thousand years to make it. His attention 

 had first been called to this subject by a discussion on the perforations (iO ft. 

 high at Tenby Castle, which by some were taken to be evidenced of a raised 

 beach, but by himself as the workmanship of land snails. At Plymouth, 

 where he had first avowed his conviction, he had been met with a courteous 

 laugli almost amounting to scorn, but since then he had caught snails in the 

 ■very act, and what was more be had them with him. The perforations were 

 unlike those made by any other animals, or those made by the salt of the 

 sea combined witli tlie carbonic acid of tlie atmosphere. At Boulogne bis 

 attention had been called to the odd appearance of the rocks by the road 

 side, and on stopping to examine it he bad found the snails actually at work. 

 The rocks were carboniferous lime-stone, and what was also remarkaljle, 

 they were in a neighbourhood that oflcred abundant food for the snails. 

 These perforations were never found where the rain and frosts could operate, 

 but always having the apertures downwards. They were never to be found 

 in the south-west projecting towards the stormy region, but under the first 

 projecting sheltered rock where there are pastures for the snails, there you 

 will find them. How he had come at the time taken by the snails to com- 

 plete a certain depth was from bis having last summer visited Risborough 

 Castle, where he found perforations such as he bad spoken of, but none more 

 than an inch deep. Now the Romans had left this 1,500 years ago, and pre- 

 suming that the snails took possession at their exit, they have worked at the 

 rate of one inch in a thousand years. This fornie-d his chronometer. How 

 he had ascertained that they worked by means of an acid was from taking 

 a snail in the fact, and not having chemical tests with him, a lady had de- 

 voted a piece of the beautiful purple ribbon of her bonnet to the enquiry, 

 and on gently stimulating the snail, the jinrple had, by means of the crea- 

 tures emission, been turned as beautiful a red as ever adorned the gills of a 

 turkey cock. Since then many wlio doubted his theory had believed it. 



Fossil IctJiijosaurus, near Cambridge. 



Mr. Carter, of Cambridge, exhibited to the section a magnificent fossil, 

 consisting of portions of the head and jaws of a large saurian animal belong- 

 ing to the genus Ichthyosaurus, which he recently procured from the lower 

 chalk, near Cambridge. Mr. C. stated, that the discovery of so large a por- 

 tion of the most important part of the skeleton was especially interesting, as 

 the remains of this genus of reptile were but very rarely met with in the 

 chalk formation, and bad hitherto been confined to detached bones and teeth. 

 The characters which enabled .Mr. C. to refer the present fossil to the genus 

 Ichthyosaurus were pointed out, and be then proceeded to notice those iu 

 which it was distinguished from any of the species hitherto described. The 

 name which he proposed for this new species was Icbtyosaurus camjjvlodon, 

 in reference to the i)eculiarly curved form of the teeth of the lower jaw. Mr. 

 C. mentioned, that the present fossil was also interesting as it proved that 

 the Ichthyosaurus of the chalk was diti'erent from any of the species of that 

 genus whicli had been hitherto discovered in the lias and oolitic formations ; 

 and therefore confirmed the observations of geologists, that hitherto no spe- 

 cies of fossil reptile, common to any two great geological formations, has 

 been discovered. 



Geology of New Zealand. 



Dr. Ernest Dieffexbach read an account of the geological features of 

 New Zealand. It appears from bis paper, that a mountain chain of ancient 

 stratified rocks runs through the island with dykes of greenstone, anterior to 

 the coal formation. At both sides of this chain are horizontal sedimentary 

 strata with fossil remains, shewing them to belong to a very recent formation. 

 There exists many older volcanic rocks, as basalts and agate porphyries, but 

 the most interesting feature is a chain of modern volcanic phenomena on the 

 grandest scale, a burning volcano in the centre and hot springs, resembling 

 those of Iceland and St. Michael, depositing a great quantity of siliceous silt. 

 It appeared from Dr. DietTenbach's paper, that the interior is occupied by a 

 great formation of barrenpumice stone gravel, and the coasts offer no extent of 

 level land. Dr. Buckland drew the conclusion from the nature of the rocks, 

 that the island was little suited to agriculture. 



, F.L.s. 



SECTION D. 

 Zoology and Botanv. 



Place of Meeting— Philosoplikal Society's Rooms. 



Picsideul.— The I!ev. Professor Hjlisloiv. 



Vice-Presidents.— Bishop of Nonvich; Professor E. Forbes; C. C. Bahingto 

 Bev. L. Jeuyns, F.L.S.; W. Ogllby. 



Sccretorles- (.. I.ankestcr, JI.l)., F.L.S., T. V. Wolleston. 



Committee— Professor Allman, B. Bull, Professor T. Bell, Dr. Cirpenter. W . Clear, Dr. 

 DauUeny, Dr. Falconer, Ur. Fleming, J. E. Cray, Ur. Hoopkin, K. \V. Hope, l)r. King, 

 l)r. B. Latham, B. WacAndrciv, A. Nasmylh, Professor B. Owen, Ur. Priuhard, Ur. 

 Bichardsoii, \V. Speiice, \V. Thompnoii, W. Yirrell. 



On Mons. Fi/.eau's process of etching daguerreotype plates by Mr. GoADBV. 



In a Daguerreotype portrait the black parts of the plate consist of silver, 

 the white portions of mercury, and the intermediate tint of a mixture of the 

 two , the degree of darkness or light depending upon the excess either of the 

 silver or of the mercury. 



In converting a Daguerreotype into an engraved plate it is necessary to etch 

 away tho dark parts and to leave the white untouched. The important part 

 or the process therefore, consists in the i)roiluction of a menstruum capable 

 of receiving the silver without attacking the mercury, and the fluid used for 

 this purpose is the following : — Dilute nitric acid ; nitrous acid ; chloride of 

 sodium, and nitrite of potash. 



The nitric acid is so far diluted that no decomposition can take place until 

 the mixture be heated when the cbloriile of sodium and nitrite of potash 

 are decomposed and chlorine and nitrous acid are evolved ; these attack 

 the silver and consequently those portions of the daguerreotype which are 

 undefended by the mercury, whilst the mercurial deposit becomes analogous 

 to the ordinary etching ground of engravers, and protects all those parts of 

 the plate that are covered with from the action of the corroding fluid. 



After a time those portions of the plate that have been acted upon by the 

 chlorine, iSic. become covered with a protecting coat of chloride of silver ; this 

 must be removed by dilute liquid ammonia, when the biting may be conti- 

 nued (if necessary), by a fresh supply of the mixed acid. 



The plate being now slightly bitten, it is to be inked and allowed to dry, the 

 surface is then thoroughly polished, the ink still remaining in the corroded 

 portions of the plate. It must then be gilded by the electrotype, those parts 

 alone receiving tlie gold that has been previously polished, ihe ink is then 

 dissolved out of the hollows by potash, and the gilded surface now constitutes 

 the etching ground in place of the mercury, and the biting may be continued 

 by nitric acid after the manner of engravers. It cannot be expected that the 

 above process should produce a finished picture, but slight assistance from 

 the hand of an engraver will speedily accomplish this. 



The engravings produced of the nervous systems of Aplysia and Tritonia, 

 the latter much magnified, and the nutriraental organs in situ of a caterpillar, 

 sufficiently demonstrate the successful application of the daguerreotype to the 

 purposes of Natural History ; the details being faithful and minute, and the 

 texture of the several tissues represented to an extent that is truly wonderful. 

 Guano. 



Mr. Trevelyan made a communication on the guano of the Paro islands. 

 As the supplies of this manure from the African coasts have become greatly 

 lessened, and in many parts almost exhausted, it is desirablo to look out for 

 new sources from whence it may be obtained. The guano of these islands is 

 derived from the Cormorants and is to be obtained in large quantities, whilst 

 the quality is considered to be quite equal to that obtained from Peru or 

 Ichaboe. 



SECTION E.— [Medical Science.] 

 Place of meeting — Aiiatumical Lecture. loom, iieai the Botanic Garden. 

 President -Ur. Haviland. 



Vice-Presidents— Professor Clarke; Professor Fisher; Dr. Hodgkin : Ur. Latbu 

 Secretaries— K. Sargent, M. A., M. B. I. A. i Dr. Webster. 

 Committee — Ur. Budd ; Ur. Laycock ; Dr. Meriimiin. 



SECTION F. 

 Statistics. 

 Place of meeting — Lecture Boom, Great-court, Trin-coil. 

 President— Earl Filzwilliam. M. A., F. E. S. 



Vice-Presidents— Lord Saiidon, M. P. j Colonel Sykes, F. B. S., Sir Charles Lemon, 

 Bart., F. B. S. ; Professor Prjme. 

 Secretaries-Joseph Fletcher, Esq., Dr. Cooke Taylor. 



Committee— Sir. J. Boileau, Colonel Everest, His E.xcellenry Edward Everett, J. Hey- 

 wood, F. B. S., Eaton Hodgkinson, Sir J. Johnston, Hart., Sir C. Lemon, Bart., R. 

 Moncton Milnes, II. P., G. B. Porter, M. Julien, Shafto Adair, 



Trade and Navigation of Norway 

 The first paper was read by Mr. Porter, and consisted of observations on 

 the Trade and Navigation of Norway, arranged by Mr. Richard Valpy. It 

 stated that the chief export trade of Norway consists of the produce of her 

 forests, fisheries, and mines. The most extensive forests are in the interior, 

 and chiefly are property belonging to the peasantry. For some years the 

 timber trade has been gradually changing its course ; formerly England was 

 looked upon as the chief market, and in return England retained almost the 

 exclusive trade in manufactures, but a few found its way from other coun- 



