Activerecord-sqlserver-adapter nvarchar datatype length

I’ve recently installed this adapter in hope that I can work with utf-8
encoding using the SQL Server nvarchar data type. I’ve installed and
followed the steps detailed at this uri:

I have this following migration class definition:
class CreateContacts < ActiveRecord::Migration
def self.up
create_table :contacts do |t|
t.column :organization_id, :integer, :null=>false
t.column :first_name, :nvarchar, :limit=>10, :null=>false
t.column :last_name, :nvarchar, :null=>false
t.column :title, :string
t.column :contact_type_id, :integer, :null=>false
t.column :fax, :string

def self.down
    drop_table :contacts


When I look at the generated table definition first_name column is
created has a length of 2 rather than 10. In fact all of the columns of
type :nvarchar get a length of 2. If I try what the web site
documentation has, namely:

t.column :body2_utf8, :nvarchar_max # Creates nvarchar(max)
or in my case:
t.column :first_name, :nvarchar_max, :null=>false

I get an error that says:
DBI::DatabaseError: Execute
OLE error code:80040E14 in Microsoft OLE DB Provider for SQL Server
Column, parameter, or variable #3: Cannot find data type
HRESULT error code:0x80020009

Does anyone know how I can set the maximum length of the nvarchar data
type successfully?

Thanks in advance, Calvin.