FACTS:

Petitioner  is  engaged  in  a  public  utility  business,  solely  engaged  in transporting passengers and cargoes by motor trucks,  over its authorized lines in Mindanao.  It owns a main office and branch offices.  To be found in their offices are machineries and equipment, which were assessed by the City Assessor as real properties.   
 

HELD:

Movable equipments to be immobilized in contemplation  of law must first be essential and principal elements of an industry or works without which such  industry  or  works  would  be  unable  to  function  or  carry  on  the industrial purpose for which  it was established.  We may  here distinguish
those movables, which are essential and principal elements of an industry, from  those  which  may  not  be  so  considered  immobilized  by  destination because they are merely incidental, not essential and principal.  

In the case at bar, the tools and equipments in question are by their nature not essential and principal elements of petitioner’s business of transporting passengers and cargoes by motor trucks.  They are merely incidentals.