B. TERRESTRIAL PHYSICS AND METEOROLOGY. 109 



those predicted by theory. The principal source of discord- 

 ance is probably to be found in the fact that the computa- 

 tions take account only of the pressures against the front 

 surface of the solid, while the reaction that takes place on 

 the hinder surface is partly or even totally neglected. In 

 the case of the anemometers employed for the purpose of 

 measuring the velocity of the wind, probably without a sin- 

 gle exception, their indications must be interpreted by means 

 of approximate empirical formulae; and no other method has, 

 as yet, been devised by which the indications given by press- 

 ure gauges can be compared with those given by velocity 

 meters. Of these latter instruments, the best are those 

 known as Robinson's anemometer and the Casella anemom- 

 eter. Of the pressure gauges, those most commonly in use 

 are the Ossler anemometer and Wild's anemometer. Dr. 

 Dohrandt has recently undertaken, at the instigation of 

 Dr. Wild, of St. Petersburg, an elaborate investigation, both 

 theoretical and experimental, into the sources of error pecul- 

 iar to these instruments ; and the memoir embracing his re- 

 sults, which was announced a year ago by Professor Wild, 

 seems to be the most valuable contribution to anemometry 

 that we have had occasion to regard since the appearance, in 

 1873, of Cavallero's investigations, which were noticed by us 

 at the time. (See Annual Record, 1 874, p. 104.) Unfortunate- 

 ly, Dr. Dohrandt was interrupted in his labors by a call, on 

 the part of the Russian Geographical Society, to superintend 

 the establishment of meteorological stations in Asia; but 

 Professor Wild assures us that his researches will be contin- 

 ued by the Physical Observatory, until definite conclusions 

 can be considered as established. Among the means adopt- 

 ed for comparing the actual velocity of the wind with the 

 readings of the anemometer, Dr. Dohrandt experimented first 

 with the method adopted thirty years ago by Duchemin, and 

 less thoroughly by others, and which consists in carrying an 

 anemometer attached to a locomotive, the velocity of whose 

 movement is well ascertained. The railroad from St. Peters- 

 burg to Tsarskoe Selo offered a good opportunity for the ex- 

 periment which was first made on July 1, 1871, in which the 

 average velocity of the railroad train seems to have been 

 from twenty-one to forty-eight kilometers per hour. During 

 the experiment the average velocity of the wind itself, in 



