I²C between ATTiny85 (8MHz) and Arduino Uno I keep receiving the following error in myATTiny85-Slave code below:

sketch_mar12a.ino: In function 'void setup()':
sketch_mar12a:19: error: 'class USI_TWI_S' has no member named 'onRequest'

I have downloaded TinyWireS and TinyWireS.h clearly has a public function onRequest. I opened the .ZIP file (downloaded from https://github.com/rambo/TinyWire) and drag-dropped TinyWireS folder into the Arduino libraries folder. This is how I install ALL libraries.
I am using Arduino 1.0.6
What am I doing wrong?
ATTiny85-Slave Code:
#include &quot;TinyWireS.h&quot;                  // wrapper class for I2C slave routines
#define I2C_SLAVE_ADDR  0x26            // i2c slave address (38)

byte t=10;

void setup()
{ 
   TinyWireS.begin(I2C_SLAVE_ADDR);      // init I2C Slave mode
   TinyWireS.onRequest(requestEvent);
}

void loop()
{
}

void requestEvent()
{  
   TinyWireS.send(t);
}

Arduino Uno-Master Code:
 #include &lt;Wire.h&gt;
 #define I2C_SLAVE_ADDR  0x26            // i2c slave address (38)

 void setup() 
 {
     Wire.begin();
     Serial.begin(9600);
 }

 void loop() 
 {
      byte num;

     // read 1 byte, from address 0x26
     Wire.requestFrom(I2C_SLAVE_ADDR, 1);

     while(Wire.available()) {
          num = Wire.read();
     }
     
     Serial.print(&quot;num = &quot;);
     Serial.println(num,DEC);
 }
I was able to compile your code "ATTiny85-Slave Code" without problems.

You can try to extract the contents of the ZIP archive (i.e. the library) directly to the directory where your sketch is stored. #include "TinyWireS.h" should then pick up that version.

You should also switch on verbose output for the compilation to have a look at the directory in which the code is compiled. Here you would find (at least in my older Arduino IDE version) copies of the included files. (/tmp/build... on Linux systems.) You can then make sure the proper version of the files is used. 

You can also search your drives for other copies of TinyWireS.h.