and Laboratory Methods. 



2507 



Fig. 54.— Arm bracket with 

 ratchet. 



ting sloping blocks on the brackets, or they can be 

 more steeply inclined by carrying up the shelf until 

 its front edge falls within the pin of the bracket, 

 and rests on that, inasmuch as the pin which fits 

 into a socket or hole on the underside of the shelf 

 lies from two to four inches behind the frorit edge 

 of the shelf. This pin can be concealed in many 

 ways, readily suggested by inspection. With large 

 objects the shelves may be tiered directly one above 

 the other of equal width. Besides tilting in the two 

 ways suggested above, sloped brackets are made 

 which give a less but useful inclination. Shelves 



brought close to the front of the case exhibit objects nearer the eye of the visitor, 

 and hence for objects of a uniform size, as cubes of building stones, wall cases 

 of the requisite depth with shelves of one width from top to bottom, directly 

 superimposed at equal distances, serve an admirable purpose. The shallow 



and applique effect of such cases is 

 sometimes disappointing. The case 

 loses atmosphere, and the receding 

 shelves in deeper cases from the bot- 

 tom upward produces a pleasant im- 

 pression. The bay arrangement of 

 shelving is to alternately widen and 

 narrow the shelving. Figure 53 

 presents these modes of shelving, 

 with others. 



The support of shelves in high 

 cases seems adequately secured in 

 three ways: (1) by the arm-bracket 

 (Fig. 54), and (2) the bayonet bracket 

 (Fig. 55), and (3) small bracket (Fig. 

 56), the two latter fitting upon perforated ratchet strips, the former upon a ratchet 

 strip with iron teeth. In the arm bracket, the brackets vary of course in length 

 according to the dimensions of the shelf to be supported, and as the bracket 

 lengthens the subordinate arm underneath moves 

 further and further out under the bracket, and at the 

 same time diverges, below, from it more and more, 

 thus keeping the angle of strain unchanged (see Fig. 

 54). A very satisfactory relation is obtained by mak- 

 ing the point of attachment of the lower arm one-half 

 (or the middle) the length of the bracket, and its di- 

 vergence from the bracket one-fourth of the length of 

 the latter. The teeth on the ratchet strip are one and 

 one-quarter inch apart. These brackets are cast iron, 

 are serviceable in all cases, and especially are suited 

 for the support of heavy weights. 



Fig. 55. — Bayonet Bracket showing ratchet, 

 proximal end, and reinforced bracket. 



Fig. .5U.— Short bracket, 

 showing ratchet and sup- 

 port. 



