J.J. Thomson concluded that the particles in cathode rays were negatively charged particles which he named electrons. Here's a breakdown of his findings:

* Deflection by Magnetic Fields: He observed that cathode rays were deflected by magnetic fields, indicating they carried an electrical charge.

* Deflection by Electric Fields: He further observed that the rays were deflected by electric fields, confirming their charged nature and the direction of the deflection indicated a negative charge.

* Independent of the Cathode Material: The properties of the cathode rays were found to be independent of the material used to create them, suggesting a fundamental constituent of matter.

* Mass-to-Charge Ratio (e/m): Thomson was able to calculate the ratio of the electron's charge (e) to its mass (m). This value was significantly smaller than that of ions, implying that electrons were much lighter than atoms.

Thomson's groundbreaking experiment provided the first direct evidence for the existence of subatomic particles and revolutionized our understanding of the atom.