diff --git a/tutorial/t15.geo b/tutorial/t15.geo
index 0550c78858bf22511946da6377d1975ef8bbdac4..52379bcc048df76edf1beaf2169707cc7dca9113 100644
--- a/tutorial/t15.geo
+++ b/tutorial/t15.geo
@@ -9,6 +9,10 @@
 // We start one again by including the first tutorial:
 Include "t1.geo";
 
+// We change the mesh size to generate coarser mesh
+lc = lc * 4;
+Characteristic Length {1:4} = lc;
+
 // We define a new point
 Point(5) = {0.02, 0.02, 0, lc};
 
@@ -23,34 +27,31 @@ Point(7) = {0.04, 0.18, 0, lc};
 Line(5) = {6, 7};
 Line{5} In Surface{6};
 
-// One can also embed a surface in a volume using the "Surface In Volume"
-// command:
+// One can also embed points and lines in a volume using the "Line/Point In
+// Volume" commands:
 Extrude {0, 0, 0.1}{ Surface {6}; }
-p = newp;
-Point(p) = {0.02, 0.12, 0.05, lc};
-Point(p+1) = {0.04, 0.12, 0.05, lc};
-Point(p+2) = {0.04, 0.18, 0.05, lc};
-Point(p+3) = {0.02, 0.18, 0.05, lc};
-l = newl;
-Line(l) = {p, p+1};
-Line(l+1) = {p+1, p+2};
-Line(l+2) = {p+2, p+3};
-Line(l+3) = {p+3, p};
-ll = newll;
-Line Loop(ll) = {l:l+3};
-s = news;
-Plane Surface(s) = {ll};
-Surface{s} In Volume{1};
-
-// Finally, one can also embed a point or a line in a volume using the
-// "Line/Point In Volume" command:
 
 p = newp;
+Point(p) = {0.07, 0.15, 0.025, lc};
+Point{p} In Volume {1};
 
-Point(p) = {0.025, 0.15, 0.025, lc};
 l = newl;
-Line(l) = {7, 22};
+Point(p+1) = {0.025, 0.15, 0.025, lc};
+Line(l) = {7, p+1};
 Line{l} In Volume {1};
 
-Point(p+1) = {0.07, 0.15, 0.025, lc/3};
-Point{p+1} In Volume {1};
+// Finally, one can also embed a surface in a volume using the "Surface In
+// Volume" command:
+Point(p+2) = {0.02, 0.12, 0.05, lc};
+Point(p+3) = {0.04, 0.12, 0.05, lc};
+Point(p+4) = {0.04, 0.18, 0.05, lc};
+Point(p+5) = {0.02, 0.18, 0.05, lc};
+Line(l+1) = {p+2, p+3};
+Line(l+2) = {p+3, p+4};
+Line(l+3) = {p+4, p+5};
+Line(l+4) = {p+5, p+2};
+ll = newll;
+Line Loop(ll) = {l+1:l+4};
+s = news;
+Plane Surface(s) = {ll};
+Surface{s} In Volume{1};