diff --git a/book/chapters/ocean_science.ipynb b/book/chapters/ocean_science.ipynb
index bbf8ca4..ac60009 100644
--- a/book/chapters/ocean_science.ipynb
+++ b/book/chapters/ocean_science.ipynb
@@ -29,19 +29,64 @@
     "'Why?' in mind before startingin on the 'What?' and the 'How?'\n",
     "\n",
     "\n",
-    "Let's start with an ambitious question."
+    "Let's start with an ambitious question.<br><br>"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "${\\Large \\textrm{How stable is the epipelagic ocean?}}$\n",
-    "\n",
-    "Of course this begs the question what is meant by 'stable' but before I get to that: \n",
-    "Let's anticipate a quibble about the term 'epipelagic ocean'. *Epipelagic* is more or\n",
-    "less synomymous with *photic*, the upper 200 meters of the water column where we can \n",
-    "expand to find downwelling sunlight in some degree. "
+    "${\\Large \\textrm{How stable is the epipelagic ocean?}}$"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<br><br>\n",
+    "Of course this begs the question of what is meant by 'stable'... but before I get to that\n",
+    "let's anticipate a quibble over the term 'epipelagic ocean'. *Epipelagic* is more or\n",
+    "less synomymous with *sunlit* or *photic* and it is applied as a modifier to *zone*. \n",
+    "That is, the upper 200 meter layer of the water column is the epipelagic zone; \n",
+    "this being the maximal depth of downwelling sunlight in some degree.\n",
+    "\n",
+    "\n",
+    "Downwelling sunlight is the baseline energy source for primary production by phytoplankton\n",
+    "living in the upper ocean. \n",
+    "Hence the epipelagic zone is the engine that converts solar energy into chemical energy\n",
+    "that powers the ecological food web.\n",
+    "I'm coopting the zone into *epipelagic ocean* to recognize that \n",
+    "the epipelagic zone changes in nature from one place to another. Placing shallow\n",
+    "profilers in vast quantity is prohibitively expensive; so for this project we will\n",
+    "begin with just three. But these are incredibly high-resolution sensor platforms; \n",
+    "and by virtue of having three shallow profilers to work with we can contribute\n",
+    "to our stability question in two ways. First we can do fine-scale characterization \n",
+    "at those three points. Second we can hope to identify\n",
+    "key features of the water column that might be amenable to other sensor programs, \n",
+    "particularly ARGO and satellite remote sensing of the sea surface.\n",
+    "\n",
+    "\n",
+    "Now to turn to *stability*. A list of apparent interpretive parameters includes:\n",
+    "\n",
+    "\n",
+    "- physical stability: temperature, density of water, available light\n",
+    "- chemical stability: salinity, dissolved oxygen, inorganic carbon\n",
+    "- biological stability: nutrient concentration (nitrates), particulate distribution, fluorescence, ...\n",
+    "- depth axis, scales from centimeters to 200 meters\n",
+    "- lateral structure, scales from meters to mesoscale (hundreds of kilometers)\n",
+    "- time scales: minutes to days to seasonal to annual to multi-year climatology\n",
+    "- perturbation in relation to larger phenomena\n",
+    "    - sea state, storms, temperature, upwelling, eddies, currents, terrigenous influence (runoff)\n",
+    "- perturbation in relation to small phenomena such as plankton lensing\n",
+    "- stability of stratified sub-structure\n",
+    "    - mixed layer depth, multiple clines (barocline, thermocline etcetera), lower epipelagic\n",
+    "    \n",
+    "    \n",
+    "From an empirical perspective these dimensions of stability can in many cases be seen as\n",
+    "forms of standard deviation. But that is looking ahead to strategy; and we aren't really\n",
+    "to that point yet. Hopefully one thing is clear, that by defining *stability* in this\n",
+    "multidimensional way I am ushering in a great deal of interest in the *structure* of \n",
+    "the upper ocean.\n"
    ]
   },
   {