Power to take evidence enables tax authorities to use civil court powers for evidence, inspection and production with safeguards. Section 37 grants wealth-tax authorities civil-court equivalence to order discovery and inspection, compel attendance and oath-bound examination, require production of books and documents, and issue commissions; designated investigators may exercise these powers on reasonable suspicion of concealed net wealth; impoundment of produced materials requires recorded reasons and limited retention absent higher approval; proceedings are treated as judicial proceedings for penal purposes.