$(a)$ What are canal rays? Who discovered them? What is the charge and mass of canal rays?
$(b)$ How are the canal rays different from electrons in terms of charge and mass?

(N/A) Canal rays are positively charged radiations produced in a gas discharge tube. They were discovered by $E. \text{ Goldstein}$. The charge of canal rays is positive,and their mass is approximately equal to the mass of a proton $(1 \text{ atomic mass unit})$.
$(b)$ Canal rays are positively charged,whereas electrons are negatively charged. The mass of an electron is extremely small,approximately $1/1837$ (or often approximated as $1/2000$) of the mass of a proton (canal ray).