matplotlib
diff --git a/‎examples/scales/custom_scale.py
Copy file name to clipboardExpand all lines: examples/scales/custom_scale.py
+6-8Lines changed: 6 additions & 8 deletions b/‎examples/scales/custom_scale.py
Copy file name to clipboardExpand all lines: examples/scales/custom_scale.py
+6-8Lines changed: 6 additions & 8 deletions
diff --git a/‎lib/matplotlib/axes/_base.py
Copy file name to clipboardExpand all lines: lib/matplotlib/axes/_base.py
+2-4Lines changed: 2 additions & 4 deletions b/‎lib/matplotlib/axes/_base.py
Copy file name to clipboardExpand all lines: lib/matplotlib/axes/_base.py
+2-4Lines changed: 2 additions & 4 deletions
diff --git a/‎lib/matplotlib/scale.py
Copy file name to clipboardExpand all lines: lib/matplotlib/scale.py
+14-3Lines changed: 14 additions & 3 deletions b/‎lib/matplotlib/scale.py
Copy file name to clipboardExpand all lines: lib/matplotlib/scale.py
+14-3Lines changed: 14 additions & 3 deletions
@@ -38,21 +38,19 @@ class MercatorLatitudeScale(mscale.ScaleBase):
     http://en.wikipedia.org/wiki/Mercator_projection
     """
 
-    # The scale class must have a member ``name`` that defines the
-    # string used to select the scale.  For example,
-    # ``gca().set_yscale("mercator")`` would be used to select this
-    # scale.
+    # The scale class must have a member ``name`` that defines the string used
+    # to select the scale.  For example, ``gca().set_yscale("mercator")`` would
+    # be used to select this scale.
     name = 'mercator'
 
     def __init__(self, axis, *, thresh=np.deg2rad(85), **kwargs):
         """
-        Any keyword arguments passed to ``set_xscale`` and
-        ``set_yscale`` will be passed along to the scale's
-        constructor.
+        Any keyword arguments passed to ``set_xscale`` and ``set_yscale`` will
+        be passed along to the scale's constructor.
 
         thresh: The degree above which to crop the data.
         """
-        mscale.ScaleBase.__init__(self)
+        super().__init__(axis)
         if thresh >= np.pi / 2:
             raise ValueError("thresh must be less than pi/2")
         self.thresh = thresh
 
@@ -1001,8 +1001,7 @@ def cla(self):
             x0, x1 = self._sharex.get_xlim()
             self.set_xlim(x0, x1, emit=False,
                           auto=self._sharex.get_autoscalex_on())
-            self.xaxis._scale = mscale.scale_factory(
-                    self._sharex.xaxis.get_scale(), self.xaxis)
+            self.xaxis._scale = self._sharex.xaxis._scale
         else:
             self.xaxis._set_scale('linear')
             try:
@@ -1016,8 +1015,7 @@ def cla(self):
             y0, y1 = self._sharey.get_ylim()
             self.set_ylim(y0, y1, emit=False,
                           auto=self._sharey.get_autoscaley_on())
-            self.yaxis._scale = mscale.scale_factory(
-                    self._sharey.yaxis.get_scale(), self.yaxis)
+            self.yaxis._scale = self._sharey.yaxis._scale
         else:
             self.yaxis._set_scale('linear')
             try:
 
@@ -24,6 +24,20 @@ class ScaleBase(object):
     And optionally:
       - :meth:`limit_range_for_scale`
     """
+
+    def __init__(self, axis, **kwargs):
+        r"""
+        Construct a new scale.
+
+        Note
+        ----
+        The following note is for scale implementors.
+
+        For back-compatibility reasons, scales take an `~.Axis` object as first
+        argument.  However, this argument should not be used: a single scale
+        object should be usable by multiple `~.Axis`\es at the same time.
+        """
+
     def get_transform(self):
         """
         Return the :class:`~matplotlib.transforms.Transform` object
@@ -57,9 +71,6 @@ class LinearScale(ScaleBase):
 
     name = 'linear'
 
-    def __init__(self, axis, **kwargs):
-        pass
-
     def set_default_locators_and_formatters(self, axis):
         """
         Set the locators and formatters to reasonable defaults for