Why did Hargrave box kites replace Eddy kites for some weather observations?

The Hargrave box kite replaced the Eddy kite for meteorological observations primarily due to its superior structural stability. While the Eddy kite—a tailless, diamond-shaped design introduced by William A. Eddy—was a popular and reliable flier, it was eventually superseded by the Hargrave box kite for scientific work because the latter was exceptionally steady in high winds.1

Developed by Lawrence Hargrave in 1893, the box kite (or cellular kite) was highly efficient and capable of carrying relatively heavy weights aloft. These characteristics made it ideal for lifting meteorological instruments to high altitudes. When flown in a train using piano wire for the flying line, the Hargrave design proved more effective for rigorous weather observation, remaining in use for such purposes well into the 1920s.21