ADVISORY COMMITTEE ON GEOPHYSICS 55 



duce a minimum effect within. The first is accomplished by proper 

 heaters, refrigerating machinery and automatic regulators. The 

 second is a factor which must enter into the construction of the 

 building from the outset and will add materially to its cost. 



7j. General character of laboratory bicilding. — It is here that 

 the experience of the Reichsanstalt is most valuable. The 

 arrangement consists in a general way of central isolated rooms, 

 one on each floor, with double doors, double walls and double 

 glass floors above and below, thus giving inclosed air spaces on all 

 sides of each room. Around this isolated room on each floor is a 

 corridor. Neither the central rooms nor the corridor are connected 

 with the heating plant of the building. Opening outward from this 

 corridor is a series of rooms for general work, extending completely 

 around the building. These are heated and ventilated from the 

 plant mentioned above, which should be able to maintain the tem- 

 perature constant within four or five centrigrade degrees throughout 

 the year. Be5^ond these rooms is the outside wall of the building, 

 of considerable thickness, and rendered insulating by means of per- 

 forated or porous brick, mineral wool or other suitable material. 



It is plain that this construction must furnish the most perfect 

 control of the temperature conditions which is possible in a build- 

 ing where many men are at work : — an outside insulating wall, the 

 general laboratory rooms where the temperature is maintained con- 

 stant by the circulation of air of constant temperature, a corridor 

 which is really exposed to no temperature change, and finally, 

 again inclosed within double insulating walls, an innermost room 

 where the most refined experiments can be conducted without 

 danger of temperature disturbance other than that from the body of 

 the observer against which special provision is necessary to fit the 

 conditions which obtain in each case. 



Protection from the heat of the sun on the top of the building 

 is secured by following the same general plan. So much of the 

 roof as covers rooms lighted by side windows, i. e., the general 

 laboratory rooms above described, would require to be double, and 

 contain a thick layer of insulating material. The central rooms are 

 dependent on overhead light, and the roof immediately over them 

 must therefore be of glass, also double, and protected from the di- 

 rect sunlight by a metal or tile roof, raised three or four feet above 

 the glass to admit the light with the minimum of heat, somewhat 

 as indicated in the accompanying sketch.* 



* Here omitted. 



