January 23, 1903.] 



SCIENCE. 



131 



equipped with motor-driven machines and 

 hand tools, and two mechanicians and a 

 carpenter are now at worli. The ap- 

 paratus and machinery now in use in the 

 temporary quarters is a part of the per- 

 manent equipment of the new buildings. 

 A considerable sum of money will, of 

 course, be needed to complete the equip- 

 ment. 



3. The facilities and appliances for 

 cari-ying on an experiment under the 

 proper conditions are more difficult to 

 secure than the apparatus itself. In gen- 

 eral, laboratory rooms should be well 

 lighted and ventilated, and their tem- 

 perature should be under control. The 

 windows should be double, in order that 

 the space near the windows (often the 

 most valuable in the laboratory) may be 

 warmer in cold weather and cooler in warm 

 weather, and freer from drafts of air, than 

 would be the case with single windows. 

 It should be possible quickly and con- 

 veniently to darken many if not all the 

 rooms. The temperature of the laboratory 

 should be automatically controlled by 

 thermostats, so that any temperature 

 (within certain limits) which may be re- 

 quired by a particular experiment or in- 

 vestigation may be maintained, both day 

 and night if necessary for any desired 

 period. The humidity of the air should 

 be low, so that moisture developed in the 

 room either by respiration or evaporation 

 may be absorbed by the air and carried 

 away instead of depositing on the walls 

 and furniture of the room and ap- 

 paratus. These last considerations, the 

 control of the temperature and humidity of 

 the air, are vital. Many kinds of work 

 can, ordinarily, be done only in the winter 

 months, because summer temperature and 

 summer humidity can not be controlled. 

 This involves not only long delays, but 

 perhaps a large amount of extra labor. 



This is perhaps oftenest the ease in elec- 

 trical work, but in many other instances it 

 is equally important. Apparatus, tools and 

 machines often suffer by rusting in Sum- 

 mer, in spite of the fact that the attendant 

 means to be caz-eful. Hence, in a labora- 

 tory where work is to be carried on during 

 the entire year, and where a large quantity 

 of valuable apparatus and instruments of 

 precision are in use, and where, in addi- 

 tion, valuable apparatus is to be received 

 from outside for testing, the necessity of 

 controlling the humidity as well as the 

 temperature of the room is evident. 



The temperature of a room may be 

 automatically controlled by means of a 

 thermostat, using either steam or hot air 

 for heating. Hot air, however, possesses 

 three important advantages over steam. 

 In the first place, steam pipes occupy valu- 

 able space in a laboratory, usually near the 

 windows or along the walls, where appa- 

 ratus or benches would otherwise be placed. 

 If they are of iron, their magnetization 

 by the earth's field changes with their 

 temperature, and since the temperature of 

 the room is regulated automatically by 

 shutting off and readmitting the steam, 

 this causes frequent and annoying changes 

 in the magnetic field Avithin the room. In 

 the second place, heating by air affords 

 the best possible ventilation, which is apt to 

 be insufficient in a steam-heated building. 

 And in the third place, heating by air en- 

 ables the temperature to be automatically 

 controlled in the summer as well as in 

 winter if facilities are provided for cool- 

 ing the air, and at the same time the hu- 

 midity may be controlled by partially 

 drying the air. The air of an unventilated 

 laboratory soon becomes saturated with 

 moisture due to respiration and evapora- 

 tion; and if it be ventilated by allowing 

 hot, moist air from without to enter, the 

 humidity rises as the temperature falls 



