18 DEPARTMENTAL REPORTS. 



for this has already been made, but the storm-warning fund will per- 

 mit of no considerable extension of the woi'k beyond finishing mat- 

 ters left over from last year. 



There are now 109 storm-warning and 9 special stations at which 

 the steel towers have been installed. Of these, 48 now need lanterns, 

 which will be issued as soon as delivered by the contractor. 



TESTING AND ADJUSTING INSTRUMENTS. 



This important work has grown to very great proportions with the 

 large extensions of the service during the past few years. 



All automatic instruments and registers, not only new instruments, 

 but old ones that have been repaired, ai-e most carefullj^ tested in 

 actual work and adjusted before the instruments are put in operation 

 at stations. But few of the observers have that intimate knowledge 

 of the theory of all these apparatus or the skill that is required to set 

 in order instruments that may be generallj' out of adjustment. This 

 delicate and important work is performed, under the direction of Pro- 

 fessor Marvin, in a most conscientious and intelligent manner by Mr. 

 Charles B. Tuch, whose skill and long experience with meteorological 

 apparatus renders his service of the greatest value. 



The comparison of thermometers likewise involves a large amount 

 of j)ainstaking, technical work. During the year about 1,400 ther- 

 mometers were inspected and compared. The temperatures at which 

 comparisons are made range from 40° below zero to 112° above, and 

 thermometers are compared at points every 10° along the scale, with 

 the exception of maximum thei*mometers, which are not compared at 

 below 32°. This means at least nine readings on every thermometer 

 and four to six additional readings at low temperatures on all mercu- 

 rial and alcohol thermometers, making an average of about thirteen 

 readings for each thermometer. This work and that of deducing and 

 tabulating the corrections from the thousands of readings involved is 

 performed in the most satisfactory manner by Mr. Samuel A. Potter. 



It is onlj' bj' such a rigid system of inspection, testing, comparison, 

 and adjustment of instrumental apparatus that a high standard of 

 excellence and accuracy can be maintained, and it may fairly be 

 affirmed that the instruments of the United States Weather Bureau 

 are unsurpassed in respect to their uniform excellence and accuracy 

 by similar instruments anywhere. 



MACHINE SHOP. 



During the past year the old, antiquated foot lathes, formerly con- 

 stituting the entire equipment of our repair shop, were replaced by 

 new power-driven lathes and some other machinery. 



The repair work on instruments fell considerably in arrears during 

 the period of transition from the old to the new machinery, not only 

 because of the time required in the installation and refitting of the 

 shop, but from the fact that the complete utility of the new machinery 

 depends upon securing a multitude of special tools, cutters, dies, jigs, 

 etc. , suited to the particular work in hand ; and a great deal of time 

 was expended in the construction of such special tools. Therefore 

 the full value of our improved equipment will only be realized as 

 these special accessories multiply and become inore varied with con- 

 tinued work, 



