i<X>3- Annual Repori of mi Direi TOR. 185 



been placed in drawers beneath the corresponding exhibition 

 material. The mineral specimens available for exchange, to the 

 number of several hundred, have been carefully assorted and 

 arranged in drawers by species, so as to be preserved from injury 

 and made readily available. The work of preparing for exhibition 

 the large Dinosaur specimen collected in 1901 has been continued 

 to completion during the year. One cervical and seven dorsal 

 vertebrae, eighteen ribs, and the sacrum have been thus prepared, 

 and so far as available case room would permit, placed on exhi- 

 bition, together with parts of the individual previously worked 

 out. The vertebral series, as now exhibited, measures about 

 thirty feet in length. Important contributions to a knowledge 

 of the structure of Dinosaurs have resulted from the working 

 out of this individual, and it forms a unique specimen. Portions 

 of another large Dinosaur individual belonging to a new genus, 

 are now being prepared for exhibition and study. The progress 

 of the work upon these fossils has been much facilitated by 

 the introduction of a complete pneumatic apparatus, including 

 drills, chisels, and rotary appliances driven by pneumatic power, 

 by which means removal of the matrix can be accomplished 

 much more safely and rapidly than could otherwise have been the 

 case. The essential tool is a pneumatic hammer of the straight 

 cylinder type. It consists of a cylindrical chamber in which a five- 

 eighth inch stroke is caused to play upon the head of a chisel at the 

 rate of 3,000 to 3,500 strokes per minute. This rapid succession of 

 light blows gives the chisel a remarkable cutting capacity, and has 

 the great advantage for paleontological work of avoiding the jar 

 attendant upon the use of the hand hammer. Considerable time has 

 been given to rearranging, cleaning, and labeling the economic collec- 

 tions. Many of the lead ores formerly exhibited in Hall 72 were 

 transferred to the West Dome, thus affording space for the exhibition 

 in Hall 72 of gold and silver ores which had hitherto been kept in 

 storage. All of the specimens in this Hall have been mounted upon 

 exhibition blocks, and labels to the number of over two thousand have 

 been provided for them. The specimens were thoroughly cleaned at 

 the same time, and dust leaks in the cases stopped as far as possible. 

 In Skiff Hall, all the specimens were removed from the cases and 

 given a thorough cleaning, rearrangement, mounting, and labeling. 

 This work was performed primarily in order to brace the shelves to 

 prevent their sagging, and accordingly the opportunity to improve 

 the collection as a whole was made use of. There were also prepared 

 in connection with the ores of the different metals, several series rep- 



