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Article A BRIEF SYSTEM OF CONCHOLOGY. ← Page 2 of 4 →
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A Brief System Of Conchology.
the solvent , retains the exact figure of the shell ; and , on being viewed through a microscope , exhibits satisfactory proofs of a vascular and organicai structure . He shows thjt this membranous substance is an appendix to the body of the animal , or a continuation of the tendinous fibres that compose the ligaments by which it i ; fixed to its shell ; and that this last owes its hardness to the earthy particles conveyed
through the vessels of the animal , which fix themselves into , and inr crust , as it were , the meshes f rmed by the reticular filaments of which this membranous substance is composed . In the shell , called porcelain ' , in particular , the delicacy of these membranes was so great , that he was obliged to put it into spirit of wine , to which he had the patience to add a single drop of spirit of nitre clay by day ,
for the space of two months ; lest the air generated , or let loose by the action of the acid on the ' earthy substance , should tear the com-r pages of its fine membranous structure into shatters ; as it certainly would have done in a more hasty and less gentle dissolution . The delicate reticulated film , left after this operation , had all the tenuity of a spider ' s web ; and accordinglhe does not attempt to delineate its
y organization . In other shells he employed even five or six months in demonstrating the complicated membranous structure of this animalsubstance by this kind of chemical anatomy . In general , however , the process does not require much time .
Of the many singular configurations and appearances of the membranous part of different shells , which are described in this memoir , and are delineated in several ' well-executed plates , we shall mention only , as a specimen , the curious membranous structure observed in the lamina ? of mother-of-pearl , and other shells of the same kind , af'er having been exposed to the operation of the author ' s solvent
^ , Beside the great variety of fixed or permanent colours with which he found the animal-filaments of these shells to be adorned , it is known , that the shell itself presents to the view a succesrion of rich and changeable colours , the production of which he easily explains from the configurations of their membranes . Nature , he observes , always magnificent in her desi ns , but singularly frugal in the execution of
them , ' produces these brilliant decorations at a-very small expence . The membranous substance above-mentioned is plaited and rumpled , as it were , in such a manner , that its exterior lamina . ' , incrusted with their earthy and semi-transparent matter , form an infinite number of little prisms , placed in all kinds of directions , which refract the rays of li ght , atnd produce all the changes of colour observable in these shells .
With respect to the figures and colours of shells , it is observed , that river shells have not so agreeable ' of diversified a colour as the land and sea shells ; but the variety in the figure , colours , and other characters of sea-shells , is almost infinite . The number of distinct species we find in the cabinets of the curious is very great ; and doubtless the deep bottoms of the sea , and the shoresyet unexplored , contain multitudes still unknown to us . Even the same species differ in some degree in almost every individual ; so that it is rare to find any two shells which are alike , in all respects .
Note: This text has been automatically extracted via Optical Character Recognition (OCR) software.
A Brief System Of Conchology.
the solvent , retains the exact figure of the shell ; and , on being viewed through a microscope , exhibits satisfactory proofs of a vascular and organicai structure . He shows thjt this membranous substance is an appendix to the body of the animal , or a continuation of the tendinous fibres that compose the ligaments by which it i ; fixed to its shell ; and that this last owes its hardness to the earthy particles conveyed
through the vessels of the animal , which fix themselves into , and inr crust , as it were , the meshes f rmed by the reticular filaments of which this membranous substance is composed . In the shell , called porcelain ' , in particular , the delicacy of these membranes was so great , that he was obliged to put it into spirit of wine , to which he had the patience to add a single drop of spirit of nitre clay by day ,
for the space of two months ; lest the air generated , or let loose by the action of the acid on the ' earthy substance , should tear the com-r pages of its fine membranous structure into shatters ; as it certainly would have done in a more hasty and less gentle dissolution . The delicate reticulated film , left after this operation , had all the tenuity of a spider ' s web ; and accordinglhe does not attempt to delineate its
y organization . In other shells he employed even five or six months in demonstrating the complicated membranous structure of this animalsubstance by this kind of chemical anatomy . In general , however , the process does not require much time .
Of the many singular configurations and appearances of the membranous part of different shells , which are described in this memoir , and are delineated in several ' well-executed plates , we shall mention only , as a specimen , the curious membranous structure observed in the lamina ? of mother-of-pearl , and other shells of the same kind , af'er having been exposed to the operation of the author ' s solvent
^ , Beside the great variety of fixed or permanent colours with which he found the animal-filaments of these shells to be adorned , it is known , that the shell itself presents to the view a succesrion of rich and changeable colours , the production of which he easily explains from the configurations of their membranes . Nature , he observes , always magnificent in her desi ns , but singularly frugal in the execution of
them , ' produces these brilliant decorations at a-very small expence . The membranous substance above-mentioned is plaited and rumpled , as it were , in such a manner , that its exterior lamina . ' , incrusted with their earthy and semi-transparent matter , form an infinite number of little prisms , placed in all kinds of directions , which refract the rays of li ght , atnd produce all the changes of colour observable in these shells .
With respect to the figures and colours of shells , it is observed , that river shells have not so agreeable ' of diversified a colour as the land and sea shells ; but the variety in the figure , colours , and other characters of sea-shells , is almost infinite . The number of distinct species we find in the cabinets of the curious is very great ; and doubtless the deep bottoms of the sea , and the shoresyet unexplored , contain multitudes still unknown to us . Even the same species differ in some degree in almost every individual ; so that it is rare to find any two shells which are alike , in all respects .