26In the following provisions of the Clean Air Act 1968 (which provide that a person who commits an offence mentioned in any of those provisions is liable on summary conviction to a fine not exceeding £100), namely—
(a)section 1(1) (which prohibits the emission of dark smoke from any industrial or trade premises);
(b)section 2(2) (which penalises the emission of grit or dust, from a chimney serving a furnace to which the section applies, at a rate exceeding a prescribed limit);
(c)section 2(4) (which penalises a failure to use any practicable means of minimising the emission of grit or dust from a chimney for which no limit is prescribed);
(d)section 3(3) (which penalises the use of certain furnaces which are not fitted with appropriate plant for arresting grit and dust);
(e)section 4(7) (which penalises the use for certain purposes of furnaces which are exempt from the operation of section 3(1) of that Act); and
(f)section 6(1) and (2) (which penalise the use of certain furnaces unless they are served by chimneys of approved heights and any conditions of the approvals are complied with),
for the word " £100 " there shall be substituted the word " £400 "
27In section 9(1) of that Act (under which a person who acquires or sells by retail any unauthorised solid fuel for use in a smoke control area is liable on summary conviction to a fine not exceeding £20) for the word " £20 " there shall be substituted the word " £100 ".