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54. A NEw INSTRUMENT to determine time, longitude, and lati- 
tude, by Saegmuller. 
55. ENGINEERS’ TRANSIT, with “ solar,’ 
num, by Saegmuller. 
> 
made of silver alumi- 
DEPARTMENT OF MECHANICS. 
In charge of Prof. R. S. Woodward. 
56. Model of INTERNATIONAL PROTOTYPE METRES. 
57. Model of INTERNATIONAL PROTOTYPE KILOGRAMMES. 
These Prototype Metres and Kilogrammes have been adopted 
as standards of length and mass, respectively, by nearly 
allnations. They were adopted as the official standards of 
the United States April 5, 1893. 
58. AUTOMATIC MERCURY VACUUM PUMP. Designed by Pro- 
fessor Pupin. 
59. Models of FORCING AND LIFTING PUMPS. 
60. Model of BRAMAH’S HYDROSTATIC PRESS. 
61. Two forms of GYROSCOPES. 
62. HYPOCYCLOIDAL LINK. 
63. PARALLEL LINK MOTION MACHINE. 
64. Aggregation of different kinds of GEARING. 
65. ELLIPTICAL GEARING. 
66. IRREGULAR GEARING. 
67. FERGUSON’S PARADOX. 
68. “ MULTIPLE GEARING.” 
DEPARTMENT OF EXPERIMENTAL PSYCHOLOGY. 
In charge of Dr. Livingston Ferrand. 
69. SPECIAL APPARATUS FOR THE DETERMINATION OF THE 
AFTER-IMAGE THRESHOLD. Designed by Mr. S. I. Franz, 
Columbia College. This apparatus is used to give stimuli of 
light, (a) of different intensities, (b) of different areas, and (c) of 
different lengths of exposure, to the eye of an observer. 
