soaked in thin plaster may be laid over the bone, first covering it with thin paper in order that the plaster jacket may simply stiffen and not adhere to it. Collecting has not always been carried on in this systematic manner, for the development of the present methods has been the result of years of experience; formerly there was a mere skimming-over of the surface in what Professor Marsh used to term the potato-gathering style, but now the effort is made to remove specimens intact, often imbedded in large masses of rock, in order that all parts may be preserved. We will take it for granted that our specimens have safely passed through all perils by land and water, road and rail; that they have been quarried, boxed, carted over a roadless country to the nearest railway, and have withstood 2,000 miles of jolting in a freight-car. The first step in reconstruction has been taken; the problem, now that the boxes are reposing on the work-room floor, is to make the blocks of stone give up the secrets they have guarded for ages, to free the bones from their enveloping matrix in order that they may tell us something of the life of the past. The method of doing this varies with the conditions under which the material has been gathered, and if from hard clay, chalk, or shale, the process, though tedious enough at best, is by no means so difficult as if the specimens are imbedded in solid rock. In this case the fragments from a given section of quarry must be assembled according to the plan which has been carefully made as the work of exhumation progressed, all pieces containing bone must be stuck together, and weak parts strengthened with gum or glue. Now the mass is attacked with hammer and chisel, and the surrounding matrix slowly and carefully cut away until the contained bone is revealed, a process much simpler and more expeditious in the telling than in the actuality; for the preparator may not use the heavy tools of the ordinary stone-cutter: sometimes an awl, or even a glover's needle, must suffice him, and the chips cut off are so small and such care must be taken not to injure the bone that the work is really tedious. This may, perhaps, be better appreciated by saying that to clean a single vertebra of such a huge Dinosaur as Diplodocus may require a month of continuous labor, and that a score of these big and complicated bones, besides others of simpler structure, are included in the backbone. The finished specimen weighs over 120 pounds, while as originally collected, with all the adherent rock, the weight was twice or thrice as great. Such a mass as this is comparatively small, and sometimes huge blocks are taken containing entire skulls or a number of bones, and not infrequently weighing a ton. The largest single specimen is a skull of Triceratops, collected by Mr. J. B. Hatcher, which weighed, when boxed, 3,650 pounds.